Retatrutide Weight Loss Results: Every Phase 3 Dose and Multi-Dose Trial

Affiliate disclosure: The RX Index may earn a commission from some links on this page, and those links are labeled. It does not change which trial numbers we report or how we report them. Retatrutide is not sold, ranked, or recommended here. It is investigational, and it cannot be legally sold or marketed for human use.

The best single retatrutide weight loss result to remember is an average 28.3% body weight loss at 80 weeks on the 12 mg dose — about 70 pounds from the trial's average starting weight of 248 pounds. The stricter result that counted everyone was 25.0%. A selected subgroup reached 30.3% at 104 weeks. Those numbers are all real. They answer different questions.

That second number is why this page exists.

If you've been reading about retatrutide weight loss results, you've probably seen one number. Maybe 24%. Maybe 28.7%. Maybe “30% — same as bariatric surgery.” All three are real. None of them means what most articles imply.

Here's the short version, then we'll show you the receipts.

The three retatrutide results everyone mixes up

All three came from the same trial program. They answer three different questions. Most articles pick the biggest one and stop.

We're not going to do that.

Is this page for you?

Yes, if you want:

• The real number for each Phase 3 dose — 4 mg, 9 mg, and 12 mg
• What that number looks like in pounds at your starting weight
• How it stacks up against Zepbound and Wegovy when the same kind of analysis is used
• Whether you can get it now
• Every completed randomized multi-dose human trial with a public body-weight result, including the early 12-week study most pages miss

No, if you want:

• A weight-loss prediction for you personally. Averages can't do that.
• A dosing guide. There is no FDA-approved dose.
• Somewhere to buy it. We don't sell it and we won't send you to anyone who does.
• A direct head-to-head verdict. TRIUMPH-5 is ongoing and has not reported results.

The RX Index is an independent GLP-1 decision resource that compares treatment paths on clinical legitimacy, care quality, transparency, access, and cost, so readers can choose the path that fits their situation.

Jump to: Every result · By dose · In pounds · Why the numbers differ · How fast · Vs. Zepbound and Wegovy · Side effects · Can you get it · Muscle · If you stop · FAQ

What are the latest retatrutide weight loss results?

Across the seven completed Phase 2 and Phase 3 efficacy trials with public body-weight results, the highest-dose average ran from 16.8% to 28.7%, depending on who was studied and how long treatment lasted. The largest general-obesity trial is TRIUMPH-1: 28.3% at 80 weeks on 12 mg in 2,339 randomized adults without diabetes. Retatrutide is investigational and is not FDA-approved.

There was also an earlier 72-person Phase 1b multi-dose trial. It reported a placebo-adjusted loss of 8.96 kg in its highest escalating-dose group after 12 weeks. That is the most useful published 12-week result, but it came from only 12 people assigned to that dose schedule and was reported as a placebo-adjusted kilogram difference, not as the group's raw mean percent loss.

An even earlier Phase 1 single-dose study found dose-dependent weight reduction that persisted through day 43 after one dose. Because it tested one dose rather than a weekly treatment course, it is documented in the sources but not mixed into the multi-dose results below.

Here are the completed randomized multi-dose human studies with public body-weight results, plus the prespecified TRIUMPH-1 extension result. We pulled each number from the original publication or sponsor result document, not from news coverage.

Sources: Coskun et al., Cell Metabolism 2022; Urva et al., The Lancet 2022; Rosenstock et al., The Lancet 2023; Jastreboff et al., NEJM 2023; TRANSCEND-T2D-1, The Lancet 2026; and Eli Lilly's TRIUMPH-1, -2, -3, and -4 releases. All were opened and checked directly on August 7, 2026.

Why several results have two official numbers

This is the single most useful thing on this page, so we're going to slow down.

Several late-stage drug trials report results two ways. Both are official. Both come from the same trial. They answer different questions.

Number one: the efficacy estimand. In Lilly's TRIUMPH releases, this estimates what would have happened if all randomized participants had remained on the study treatment, while allowing dose interruptions and changes, and without starting prohibited weight-management treatment. Plain version: this is the trial's best estimate of the drug's effect if assigned treatment continued.

Number two: the treatment-regimen estimand. Lilly defines this as the average treatment effect regardless of whether people stayed on the study treatment or started prohibited weight-management treatment. Plain version: this keeps people in the result even if they stopped treatment.

The efficacy number is usually bigger. It is also the number most likely to run in a headline.

The treatment-regimen number is the stricter start-to-finish trial result. It is not the same thing as a real-world effectiveness study, because trial participants still received structured follow-up and were not a random sample of everyone who might use the drug.

Our finding: the gap widened with dose in TRIUMPH-1

We put both numbers side by side for every dose in the three completed trials that published both. Then we subtracted.

Our calculation using the published figures. Subtraction may differ by 0.1 point from unrounded source data.

Look at TRIUMPH-1. The gap goes 1.4, then 2.2, then 3.3. It widens at every step up.

That pattern did not repeat perfectly in TRANSCEND-T2D-1, so it should not be turned into a universal rule. What the table proves is simpler: the number changes when the analysis changes, and the size of that change can be meaningful.

The most-quoted retatrutide number comes from the smallest completed Phase 3 efficacy trial

Now for the part that should change how you read every other article on this drug.

28.7% is the number you see everywhere. It comes from TRIUMPH-4. Which is:

• The smallest completed Phase 3 efficacy trial in this group — 445 people, versus 2,339 in TRIUMPH-1
• A knee osteoarthritis population, not a broad general-obesity sample
• A trial where 84% of participants started at BMI 35 or higher
• The trial with the highest reported adverse-event discontinuation rate among these completed efficacy trials — 18.2% in the 12 mg arm

And its own treatment-regimen number? 23.7%.

We are not saying 28.7% is fake. Lilly published it, it is real, and TRIUMPH-4 met the endpoints it was designed to test. We're saying that if you want one number to hang your understanding on, it shouldn't be that one.

Use 28.3% from TRIUMPH-1 as the main anchor. Bigger trial. Broader obesity population. Same ballpark. And keep 25.0% beside it so you can see what happened when the analysis counted outcomes regardless of treatment adherence.

And the 30.3% headline needs an asterisk

You'll see 30.3% described as “two-year results” or “surgery-level weight loss.” It is a real reported number. Here's who it describes.

The extension enrolled 532 people who:

• Started the main trial at BMI 35 or higher
• Completed the main 80-week study
• Tolerated their assigned study dose

Lilly's endnote adds that the prespecified extension used the first 532 eligible completers from participating countries who reached week 80 on study drug without discontinuation or a permanent dose reduction, still had BMI above 22 at week 80, and met the baseline BMI rule.

They continued another 24 weeks. Treatment stayed blinded, and doses could move to a maximum tolerated 9 mg or 12 mg.

People who had originally been assigned 12 mg averaged 30.3% under the efficacy analysis and 29.9% under the treatment-regimen analysis at week 104.

So 30.3% is the answer to a specific question: what happened in a selected group that had already completed 80 weeks and tolerated treatment? It is not the answer to what happens to a typical person who starts retatrutide.

Every time you see 30.3%, that asterisk belongs with it. We'll keep attaching it.

The right available GLP-1 path isn't the same for everyone — it depends on your state, insurance and formulary, whether you want an FDA-approved medication or are asking about a lawful patient-specific compounded option, your preferred treatment form, and your budget. Retatrutide is not one of the normal prescribing options. Use The RX Index's Find My GLP-1 Path tool to compare paths you can actually pursue now with source-checked pricing.

How much weight did people lose at each retatrutide dose?

In TRIUMPH-1, retatrutide 4 mg produced 19.0% average weight loss at 80 weeks under the efficacy analysis, 9 mg produced 25.9%, and 12 mg produced 28.3%. The jump from 4 mg to 9 mg delivered most of the added loss. The final step from 9 mg to 12 mg added 2.4 percentage points.

Every completed Phase 3 efficacy result by studied target dose:

These are efficacy-estimand results. Different populations and trial lengths mean the rows are not direct comparisons.

Full picture from the largest trial:

Eli Lilly TRIUMPH-1 topline release, May 21, 2026. Average starting weight: 248.5 lb. Average BMI: 40.0.

Those “lost 25% or more” rows are the honest version of social proof. They show the spread, not just the middle. At 12 mg, 62.5% of people lost at least a quarter of their body weight. They also show the other side: more than half did not reach 35%.

One more figure worth sitting with. 65.3% of the 12 mg group finished with a BMI under 30 — below the obesity threshold — including 37.5% of the people who started at BMI 40 or above. The second figure was a post-hoc analysis, so it is useful context, not a prespecified confirmatory endpoint.

What each dose step bought — and what it cost in observed discontinuation

Here's something we haven't seen assembled in one place. We took the efficacy weight loss at each dose and the adverse-event discontinuation rate at each dose across four completed registrational trials. Then we divided the extra percentage points of weight loss by the extra percentage points of discontinuation.

Our descriptive calculation from Lilly's published per-dose figures. This is not a validated clinical benefit-risk score and should not be used to choose a dose.

Two things jump out.

In TRIUMPH-1, the last step had sharply smaller returns by this simple measure. Going from 4 mg to 9 mg added 6.9 points of efficacy weight loss and 2.8 points of adverse-event discontinuation. Going from 9 mg to 12 mg added 2.4 points of weight loss and 4.4 points of discontinuation.

The 9-to-12 mg step added only 1.0 to 2.4 percentage points across all four trials. Four populations. Four designs. The added efficacy weight loss stayed inside that narrow range.

We'll flag one oddity honestly, because we noticed it and the topline release does not explain it. In TRIUMPH-2, adverse-event discontinuation went from 3.8% at 4 mg to 11.6% at 9 mg, then back down to 7.7% at 12 mg. The middle dose had more people stopping than the top dose. We're reporting it, not inventing a reason for it.

The 4 mg result nobody talks about

Here's the finding we think matters most to an actual person trying to understand the trial.

Retatrutide 4 mg was reached with one escalation step. Participants started at 2 mg, moved to 4 mg after four weeks, and stayed at the target dose.

At that dose in TRIUMPH-1, the efficacy result was 19.0% — about 47 pounds from the trial's average starting weight.

And here's the part:

In both completed Phase 3 trials that tested 4 mg, the observed adverse-event discontinuation rate was lower in the 4 mg arm than in the placebo arm.

That does not prove 4 mg is safer overall, and it does not create an approved dose. It does prove that the lowest Phase 3 target dose deserves more attention than it gets.

What does 28.3% retatrutide weight loss look like in pounds?

A percentage only becomes useful once you attach it to a starting weight. At 28.3%, a 200-pound person would lose about 57 pounds and a 280-pound person would lose about 79 pounds. This is arithmetic on a group average, not a prediction of what any individual would lose.

Retatrutide trial result translator

Use the row that matches the trial population — not the biggest number on the page.

Formula: starting weight × result percentage = approximate pounds represented by that group average

Example: You enter 240 lb, have type 2 diabetes, and look at the 12 mg result. The closest completed Phase 3 match is TRIUMPH-2. Its 20.8% efficacy result translates to about 49.9 pounds at 240 lb. It does not mean you personally would lose 49.9 pounds, and it is not the 28.3% result from the no-diabetes trial.

This translator does not predict your result. It converts a published group average into pounds at the weight you type in. Retatrutide is investigational and cannot be prescribed through normal channels.

Why no calculator can tell you your number

The arithmetic doesn't know:

• Your medical history
• How well you'd tolerate the drug
• Whether you'd stay on it
• Which target dose you would reach in a future approved label
• Your starting BMI and body composition
• Whether you have diabetes or another condition that changes the closest trial match
• What the FDA-approved dosing will eventually look like — if approval happens

A group average describes a group. That's all it can do.

Why do retatrutide results range so widely?

The numbers differ because the trials studied different people for different lengths of time, used different doses, and reported different statistical analyses. The early 12-week Phase 1b result was a placebo-adjusted kilogram difference in a tiny dose cohort. The 30.3% result was a 104-week selected extension subgroup. Those are not interchangeable.

Four things move the number.

1. Who was in the trial. This is the biggest one.

The completed trials involving type 2 diabetes reported lower average weight loss than the no-diabetes obesity trials. That pattern also appears in studies of other incretin medicines. But these are separate trials, so they cannot prove that diabetes alone caused the full gap.

2. The dose. Inside TRIUMPH-1, 4 mg and 12 mg were separated by 9.3 percentage points under the efficacy analysis.

3. How long treatment lasted. Twelve weeks, 36 weeks, 40 weeks, 48 weeks, 68 weeks, 80 weeks, and 104 weeks are not interchangeable. You cannot compare a 40-week result with an 80-week result and call it a fair fight.

4. How the result was counted. The two-estimand problem we covered above changed the TRIUMPH-4 12 mg result from 28.7% to 23.7%.

One more trap: watch the words “up to”

Lilly often uses “up to” to point to the best cell in a result table. Twice in 2026, that cell was the middle dose, not the highest dose.

Example one. The July 23, 2026 TRIUMPH-2 release said A1C fell by “up to” an average 1.6%.

That 1.6% belongs to 9 mg. The 12 mg result was 1.5%.

Example two. The March 19, 2026 TRANSCEND-T2D-1 release said A1C fell by “up to” 2.0%.

Same construction. Same result. The 9 mg dose again.

Nothing about “up to” is false. But if you assume the biggest headline number always belongs to the biggest dose, you can still walk away wrong.

How fast did retatrutide weight loss happen?

The best published obesity checkpoints are 17.5% at 24 weeks and 24.2% at 48 weeks on 12 mg in the Phase 2 obesity trial. An earlier Phase 1b study did report a real 12-week result: the highest escalating-dose cohort had 8.96 kg more weight loss than placebo. But only 12 people were assigned to that cohort, and the study did not report that figure as a raw mean percentage for the cohort.

Phase 2 obesity checkpoints:

Jastreboff et al., NEJM 2023. Least-squares mean changes.

The Phase 2 correction almost every page gets wrong

Here's a detail we'd bet money most articles you've read got backward.

17.5% at 24 weeks was the primary endpoint. The 24.2% at 48 weeks result was a secondary endpoint.

Somewhere along the way, the secondary number became “the Phase 2 result.” Check the pages telling you about retatrutide's 24.2% and see how many mention that.

Our calculation: 17.5 divided by 24.2 is about 72%. In that study, roughly seven-tenths of the 12 mg group's 48-week average loss had appeared by week 24.

What were the real three-month results?

Many retatrutide summaries say there is no verified three-month result. That is wrong.

The Phase 1b trial ran for 12 weeks in 72 adults with type 2 diabetes. In the highest retatrutide cohort, 12 people followed a 3 mg → 6 mg → 9 mg → 12 mg escalation schedule. At week 12, their placebo-adjusted weight reduction was 8.96 kg, with a 90% confidence interval from 6.75 to 11.16 kg.

That result matters. So do its limits:

• It was an early safety and dose-escalation study, not an obesity efficacy trial.
• The highest-dose cohort had only 12 people.
• The published result was a placebo-adjusted kilogram difference, not the group's raw mean percentage loss.
• It does not validate seller-made week-by-week charts or home dosing schedules.

A chart without a named trial, time point, population, and analysis is still marketing.

Did the weight loss stop?

Not by the main endpoint in the completed studies that directly addressed the pattern.

Lilly's TRANSCEND-T2D-1 release said no plateau was observed through week 40. The Phase 2 obesity paper also reported continued loss through week 48 at the higher doses.

The TRIUMPH-1 extension subgroup reached 30.3% at week 104. But the public release does not give that exact subgroup's week-80 result, so you cannot subtract 28.3% from 30.3% and claim the subgroup lost exactly two more points. The 28.3% figure came from the full 12 mg trial arm; the 30.3% figure came from selected extension participants.

Is retatrutide better than Zepbound or Wegovy?

No completed head-to-head trial has answered that. In an indirect comparison using treatment-regimen or treatment-policy results and subtracting each study's own placebo result, retatrutide 12 mg was 3.3 percentage points higher than tirzepatide 15 mg. That is a cleaner comparison than the 6-to-14-point gaps in many headlines, but it still cannot prove superiority between drugs.

Almost every comparison you'll read online has the same flaw. It puts retatrutide's efficacy number next to another drug's treatment-policy number and never mentions it.

That's timing one runner with a stopwatch and the other with a calendar.

Here is the closest comparison we can build from public data. It uses the result that counts outcomes regardless of treatment adherence, then subtracts each drug's own placebo result.

Retatrutide: Lilly TRIUMPH-1. Tirzepatide: Zepbound prescribing information. Semaglutide: Wegovy prescribing information and STEP UP. Wegovy HD 7.2 mg received FDA approval in March 2026. Different trials used different labels for closely related adherence-regardless analyses.

Three things this table shows that the headlines don't.

The closest indirect gap is 3.3 points. Retatrutide 12 mg's placebo-adjusted result was 21.1 points. Tirzepatide 15 mg's was 17.8. The difference is 3.3 points — not the 13.8-point gap created by putting 28.7% beside 14.9% from mismatched analyses and populations.

Retatrutide's lowest Phase 3 target dose lands in the middle. The 4 mg placebo-adjusted result was 13.7 points — above Wegovy 2.4 mg in this table and below Wegovy HD 7.2 mg. It took one escalation step in TRIUMPH-1, and its observed adverse-event discontinuation rate was lower than placebo.

Retatrutide also ran longer. TRIUMPH-1 lasted 80 weeks, versus 72 weeks for SURMOUNT-1 and STEP UP and 68 weeks for STEP 1. That does not erase the difference, but it is another reason not to call this a direct race.

What this table cannot prove

These are separate trials. Different people. Different sites. Different years. Different background care. Randomization protects comparisons inside a trial, not between separate trials.

The direct comparison — retatrutide against tirzepatide under the same rules — is TRIUMPH-5 (NCT06662383). It is ongoing. Until it reports, “retatrutide is better than Zepbound” is a hypothesis, not an established fact.

Anyone telling you otherwise is ahead of the evidence.

Want the method behind this comparison? Placebo-Adjusted Weight Loss Explained · How to Read GLP-1 Clinical Trials

### Before you compare drugs, check what you can actually get covered Here's the thing about a 3.3-point indirect difference: it can matter less than the difference between a medication you can afford and one you can't. Zepbound and Wegovy are approved and prescribable now. Your plan may cover one and exclude the other. Check coverage for Ozempic, Wegovy, and Zepbound — free (affiliate link) Ro says the report shows whether your plan covers those three pen products and whether prior authorization is required. The coverage check itself is free. It does not guarantee approval or a prescription.

What did people give up to get those retatrutide results?

The most common side effects were digestive and generally became more common at higher doses. In TRIUMPH-1, 42.4% of the 12 mg group reported nausea and 25.3% reported vomiting. Across the completed late-stage efficacy trials, adverse-event discontinuation varied widely by dose and population. Retatrutide has no FDA-approved safety label yet.

TRIUMPH-1, the largest trial:

Eli Lilly TRIUMPH-1 topline release, May 21, 2026.

What is dysesthesia?

Dysesthesia means an odd or unpleasant skin sensation — tingling, burning, prickling, or skin that feels strange to the touch.

Lilly said the dysesthesia events in TRIUMPH-1 were generally mild to moderate, most resolved during treatment, and most people continued taking the drug.

But here's a number worth checking. You'll see 20.9% quoted often. That figure came from the 12 mg arm of TRIUMPH-4, the 445-person knee osteoarthritis trial. The same 12 mg dose produced:

The rate varied sharply across trials. That is more useful than treating the highest observed number as a universal expectation.

About the 18.2% discontinuation figure

TRIUMPH-4's 12 mg group had the highest reported adverse-event discontinuation rate in the completed efficacy trials summarized here.

Two things belong with that number.

First, Lilly said the discontinuation figures included people who stopped because they believed they had lost too much weight.

Second, the observed rate was lower among participants who started at BMI 35 or higher: 12.1% at 12 mg and 8.8% at 9 mg.

That does not erase the full-trial rate. It shows why the starting population matters.

What the cardiovascular data did not show

TRIUMPH-3 enrolled people with severe obesity and established cardiovascular disease. It reported prespecified analyses of major cardiovascular events, but it was not a dedicated cardiovascular-outcomes trial powered to prove a reduction in heart attacks or strokes.

Both confidence intervals cross 1.0. In plain language: these results did not establish a cardiovascular benefit.

Retatrutide has not been shown to reduce heart attacks or strokes. Anyone describing it as heart-protective is going past the evidence.

For contrast, Wegovy already has an FDA-approved indication to reduce the risk of cardiovascular death, heart attack, and stroke in adults with cardiovascular disease and either obesity or overweight. See Best GLP-1 for Cardiovascular Protection.

What TRIUMPH-3 did report at 12 mg: triglycerides down 37.0%, high-sensitivity C-reactive protein down 51.2%, systolic blood pressure down 9.3 mmHg, and waist circumference down 7.5 inches. Those are risk factors. Risk factors are not clinical outcomes.

Can you get retatrutide right now?

Retatrutide is not FDA-approved and cannot be prescribed through normal commercial channels. A clinical trial remains the main legitimate access route. A narrow single-patient expanded-access pathway is also listed for adults with refractory obesity who meet strict criteria and cannot join a suitable trial. A doctor must submit the request.

The expanded-access pathway, in plain terms

ClinicalTrials.gov lists NCT07629401 as a pre-approval, single-patient expanded-access pathway for retatrutide.

The listed patient criteria include all of these:

• Age 18 or older
• Refractory obesity with BMI 35 or higher despite adherence to and tolerance of the highest available dose of an approved chronic weight-management medicine
• At least two serious or life-threatening obesity-related complications that are under medical care
• Inability to join a retatrutide trial or a comparable study because of eligibility or lack of an accessible site
• Discussion of standard treatment options, including bariatric surgery, through shared decision-making
• No known reason the patient should not receive retatrutide under the protocol

This is not early access for people who simply want a stronger weight-loss medicine. It is a narrow path for severely ill patients who have exhausted available options and cannot join a trial.

The treating physician has to submit the request. The patient cannot order or apply for the medicine directly. Lilly reviews requests individually, and access still depends on eligibility, geography, supply, and regulatory steps.

When might retatrutide be approved?

Lilly said on July 23, 2026 that it plans to submit a Biologics License Application in the first quarter of 2027. That is the manufacturer's planned filing window, not an approval date.

A planned filing is not an approval. FDA review comes after submission. There is no announced approval date, launch date, final approved dose schedule, or list price.

What about the retatrutide being sold online?

Short answer: it is not an FDA-approved retatrutide treatment, and it is not the Lilly product used in these trials.

Three facts, then we'll move on.

One. FDA says retatrutide cannot be used in compounding under federal law. It is not a component of an FDA-approved drug and has not been found safe and effective for any condition.

Two. Writing “research use only” on a vial does not turn it into a lawful human treatment. Lilly says retatrutide cannot be legally sold or marketed for human use.

Three. A product sold outside an authorized trial or expanded-access process has not gone through FDA review for identity, strength, purity, sterility, effectiveness, or labeling. A buyer cannot assume the vial contains the same molecule, dose, or manufacturing quality used in the trials.

The numbers on this page describe a specific investigational molecule made under controlled pharmaceutical manufacturing, given at measured doses, and monitored inside research protocols. They do not describe an online vial.

One thing you should know about us: several sites publishing retatrutide results also sell peptides or send readers to peptide sellers. We don't sell peptides, we have no relationship with any peptide seller, and we never will.

See our dated Compounded GLP-1 Enforcement Tracker.

### Retatrutide is a 2027 filing question. Your weight is a today question. If you've read this far, you already know the honest answer: for almost everyone reading this, retatrutide is not a normal treatment option in 2026. Lilly plans to file in early 2027, and FDA review comes after that. That doesn't mean waiting is your only move. FDA-approved weight-management medicines with published trial data are available now, and the cleanest indirect gap between the strongest approved injectable and retatrutide is smaller than the internet makes it look. Get your personalized GLP-1 action plan — about 60 seconds, free Answer a few questions about your state, insurance, preferred treatment form, and budget. Find My GLP-1 Path compares available treatment paths with source-checked pricing. No signup wall.

How much of the retatrutide weight loss was fat, and how much was lean mass?

Only one published retatrutide body-composition substudy has measured this with DXA. It included 189 adults with type 2 diabetes at 36 weeks. Across the pooled 4 mg, 8 mg, and 12 mg groups, the fat-loss index was 64.6% — meaning about 65% of the measured weight loss was fat mass and about 35% was lean soft tissue. No Phase 3 body-composition result has been published.

The published details:

• Total fat mass fell 26.1% at 8 mg and 23.2% at 12 mg
• Lean mass fell by as much as 6.5 kg in a treatment group
• The pooled fat-loss index was 64.6% across the 4 mg, 8 mg, and 12 mg groups

Coskun et al., The Lancet Diabetes & Endocrinology, 2025. PMID 40609566.

Two honest corrections matter here.

“Lean mass” is not the same as “skeletal muscle.” DXA separates bone mineral from soft tissue, then divides soft tissue into fat mass and lean soft tissue. Lean soft tissue includes skeletal muscle, but it also includes organs, connective tissue, and body water. A DXA result cannot tell you that every pound of lean tissue lost was muscle.

And this was 189 people with type 2 diabetes at 36 weeks. It is not the 2,339-person, 80-week obesity population that produced the 28.3% headline. No published Phase 3 result proves that retatrutide preserves muscle or tells us the fat-to-lean split at 28.3% total weight loss.

For the cross-drug picture, see GLP-1 Lean Mass Loss by Drug.

What happens to retatrutide results if you stop taking it?

No retatrutide withdrawal study has published results yet. With semaglutide, participants in the STEP 1 extension regained about two-thirds of their prior loss within one year of stopping treatment and the lifestyle program. With tirzepatide, people switched to placebo in SURMOUNT-4 gained 14.0% over the next 52 weeks, while people who continued treatment lost another 5.5%.

This is the part of the story that decides whether any of these numbers matter to you.

Here's what the older drugs showed:

• Semaglutide: participants in the STEP 1 extension had lost 17.3% at week 68. One year after treatment and the structured lifestyle intervention stopped, they had regained 11.6 percentage points — about two-thirds of the prior loss.
• Tirzepatide: after a 36-week open-label lead-in, participants switched to placebo gained 14.0% over the next 52 weeks, while those who continued tirzepatide lost another 5.5%.

Retatrutide may or may not follow the same exact pattern. There is no published withdrawal result yet, so nobody can honestly give you a retatrutide regain percentage.

Which reframes the whole question.

The number that ends up on your scale isn't decided only by which drug has the biggest trial result. It is also decided by which treatment you can get, tolerate, afford, and continue.

A bigger trial number does not help if the treatment is unavailable or impossible for you to stay on.

One thing we'll say plainly

If your priority is the lowest possible monthly sticker price, an FDA-approved medication through Ro may not be your cheapest path. Ro charges a membership fee, medication costs extra, and some other cash-pay programs or lawful patient-specific compounded prescriptions may list a lower price. Compounded drugs are not FDA-approved, and federal law limits when copies of approved drugs can be compounded.

But that limitation is exactly the point of this page.

Ro's weight-management program focuses on FDA-approved medication options. That means the drugs it prescribes have FDA-reviewed labels with dose, safety, and trial data behind them — the same kind of evidence you just spent this page looking for.

### If staying on treatment is what makes the number real, start by pricing the full path Ro Body membership is $39 for the first month, then $149 month to month or as low as $74 per month with an annual plan paid upfront. Medication costs extra. See Ro's current membership and medication pricing (affiliate link · pricing verified August 7, 2026)

What's still coming for retatrutide?

Five Phase 3 retatrutide studies have now produced public topline or peer-reviewed results: TRANSCEND-T2D-1 and TRIUMPH-1 through TRIUMPH-4. The main TRIUMPH-1, -2, -3, and -4 efficacy reports have not yet appeared as full peer-reviewed journal articles. Major studies are still running for direct comparison with tirzepatide, maintenance, cardiovascular and kidney outcomes, liver outcomes, and chronic low back pain.

The TRIUMPH-1 knee osteoarthritis and obstructive sleep apnea basket-trial results were reported separately in June 2026. They are no longer “still to be released.”

That last table row deserves its own sentence.

Most of the new Phase 3 weight-loss numbers on this page still come from sponsor releases, not full peer-reviewed papers. Lilly's releases provide detailed tables and are materially useful, but a sponsor topline release is not the same as a complete journal report reviewed by outside experts.

The peer-reviewed retatrutide record now includes more than two datasets:

• Phase 1 single-dose pharmacology — Cell Metabolism, 2022
• Phase 1b type 2 diabetes — The Lancet, 2022
• Phase 2 type 2 diabetes — The Lancet, 2023
• Phase 2 obesity — New England Journal of Medicine, 2023
• Phase 2a MASLD substudy — Nature Medicine, 2024
• Phase 2 body-composition substudy — The Lancet Diabetes & Endocrinology, 2025
• TRANSCEND-T2D-1 — The Lancet, 2026

Retatrutide weight loss results: your questions answered

How much weight did people lose on retatrutide? In the largest completed trial, the efficacy average was 28.3% of body weight at 80 weeks on 12 mg — roughly 70 pounds from an average starting weight of 248.5 pounds. The same trial's treatment-regimen result was 25.0%. Lower target doses produced 25.9% at 9 mg and 19.0% at 4 mg under the efficacy analysis.

Is the 30.3% result typical? No. It came from a selected 532-person extension group with baseline BMI 35 or higher who completed the main 80-week study and tolerated assigned treatment. It answers what happened in eligible completers who continued, not what happens to every person who starts.

What were retatrutide's three-month results? A 12-week Phase 1b study in 72 adults with type 2 diabetes reported 8.96 kg of placebo-adjusted weight loss in the highest escalating-dose cohort. Only 12 people were assigned to that cohort, and the result was not reported as a raw mean percent loss. No completed Phase 3 trial has published a 12-week average.

Did everyone lose 28.3%? No. It is an average under one statistical analysis. At 12 mg in TRIUMPH-1, 62.5% lost at least 25%, 45.3% lost at least 30%, and 27.2% lost at least 35% under the efficacy analysis. Individual results varied.

Does retatrutide work as well in people with type 2 diabetes? The completed diabetes trials reported lower averages: 20.8% at 80 weeks in TRIUMPH-2 and 16.8% at 40 weeks in TRANSCEND-T2D-1, versus 28.3% in TRIUMPH-1 without diabetes. Separate trials cannot prove diabetes caused the entire difference.

Is retatrutide FDA-approved? No. Retatrutide is investigational and has no FDA-approved commercial product. Lilly plans to submit a Biologics License Application in the first quarter of 2027.

Can a doctor prescribe retatrutide? Not through normal commercial prescribing. A doctor may be able to enroll an eligible patient in a clinical trial or request single-patient expanded access for a narrowly defined, severely ill patient who meets the listed criteria. Lilly and regulators still have to approve the process.

Can a pharmacy compound retatrutide? FDA says no. Retatrutide cannot be used in compounding under federal law. It is not a component of an FDA-approved drug and has not been found safe and effective for any condition.

Is retatrutide better than Zepbound? No completed direct trial has answered that. In our indirect placebo-adjusted comparison using adherence-regardless analyses, retatrutide 12 mg was 3.3 percentage points higher than tirzepatide 15 mg. TRIUMPH-5 is testing them directly.

What are the most common retatrutide side effects? Nausea, diarrhea, constipation, and vomiting were among the most common, and rates generally increased at higher doses. At 12 mg in TRIUMPH-1, 42.4% reported nausea and 25.3% reported vomiting. Dysesthesia occurred in 12.5% versus 0.9% on placebo.

Does retatrutide cause muscle loss? A 189-person Phase 2 body-composition substudy found a pooled fat-loss index of 64.6%, so about 35% of measured weight loss was lean soft tissue. Lean soft tissue is not identical to skeletal muscle, and no Phase 3 body-composition result has been published.

Will you regain weight if you stop? Retatrutide-specific withdrawal results have not been published. Semaglutide and tirzepatide withdrawal studies both showed substantial regain after treatment stopped, but they do not provide a retatrutide-specific percentage.

How much will retatrutide cost? No approved list price exists because there is no approved commercial product. Any launch price quoted now is speculation.

Is “GLP-3” the correct name? No. Retatrutide activates GIP, GLP-1, and glucagon receptors, but “GLP-3” is not a scientific drug class. Triple hormone receptor agonist or triple agonist is more accurate.

How do I find a legitimate retatrutide trial? Search ClinicalTrials.gov or Lilly's official trial directory. Check the recruitment status, site location, and eligibility rules on the actual study record. A listing does not mean every site is open or that you qualify.

How we verified these retatrutide results

We opened the original publications, Eli Lilly's result releases, FDA pages, current prescribing information, ClinicalTrials.gov records, and the live Ro pricing pages. Every trial percentage on this page is tied to a primary document. Where we did our own arithmetic, we labeled it and showed the inputs.

What we verified on August 7, 2026:

• The Phase 1 single-dose publication — dose-dependent weight reduction that persisted through day 43 after one dose
• The Phase 1b publication — 72 enrolled participants, the 12-person highest escalating-dose cohort, and the 8.96 kg placebo-adjusted week-12 result
• The Phase 2 type 2 diabetes publication — 281 participants and the 36-week body-weight results
• The Phase 2 obesity publication — including that 17.5% at 24 weeks was the primary endpoint and 24.2% at 48 weeks was secondary
• TRANSCEND-T2D-1 — weight and A1C results under both estimands and the peer-reviewed 2026 publication
• TRIUMPH-1 — both estimands, responder rates, waist change, adverse events, discontinuation, dosing steps, and extension design
• TRIUMPH-2 and TRIUMPH-3 — per-dose weight results, A1C, adverse-event discontinuation, cardiovascular hazard ratios, risk-factor changes, and the planned Q1 2027 filing
• TRIUMPH-4 — both weight estimands, dysesthesia, discontinuation, and the BMI 35+ subgroup
• FDA's current retatrutide compounding statement
• The single-patient expanded-access record and its eligibility rules
• Tirzepatide and semaglutide comparison figures from current FDA-approved prescribing information and sponsor trial documents
• Ro's live membership pricing, the fact that medication costs extra, its free insurance checker scope, and its current listed medication options

What we calculated ourselves — and labeled throughout:

• The gap between the two retatrutide estimands at each dose
• The descriptive weight-loss-per-added-discontinuation ratio at each dose step
• The placebo-adjusted cross-trial comparison
• The pounds conversions
• The 72% share of the Phase 2 48-week loss present at week 24

What we could not verify from a full journal report: TRIUMPH-1, -2, -3, and -4 have not yet been published as complete peer-reviewed papers. Their figures rest on Lilly's public releases and conference reporting. The ClinicalTrials.gov record for TRIUMPH-1 has also shown an enrollment figure of 2,335, while Lilly's result release says 2,339 were randomized. We use 2,339 when describing Lilly's reported trial result and disclose the registry difference here.

What nobody knows yet: an FDA approval date, launch date, commercial price, insurance coverage rules, final approved dose schedule, long-term withdrawal result, or what any individual would lose.

Who wrote this. The RX Index Research Team. No physician reviewed this page and we're not claiming one did. Everything here is sourced so you can check it yourself.

Found an error? Corrections are checked against the primary source. Material changes are logged below with the old value, the new value, and the date.

Change log

The bottom line

Retatrutide's results are genuinely impressive. They're also more complicated than any headline lets on.

Here's what to carry away.

The number to remember is 28.3% at 80 weeks on 12 mg from the biggest completed general-obesity trial — with 25.0% beside it as the treatment-regimen result. Not 28.7% by itself from the smallest completed Phase 3 efficacy trial. Not 30.3% without the selected-extension asterisk.

The closest indirect, placebo-adjusted gap between retatrutide 12 mg and Zepbound 15 mg is about 3.3 percentage points. That is not a head-to-head verdict.

The 4 mg dose deserves more attention than it gets. It produced 19.0% under the efficacy analysis after one escalation step, and its observed adverse-event discontinuation rate was lower than placebo in both completed Phase 3 trials that tested it.

And almost nobody can get retatrutide now. In 2026, legitimate access is limited to clinical trials and a narrow single-patient expanded-access route. Lilly plans to file in the first quarter of 2027. FDA review comes after that.

Which leaves you with a real question, and it isn't “which drug has the biggest number?” It's this: what can you start, afford, tolerate, and continue?

Because the biggest number on the internet is useless if the treatment is unavailable to you.

### Still not sure which available GLP-1 path is right for you? Take our free matching quiz. Find My GLP-1 Path → Answer a few questions about your state, insurance, whether you want an FDA-approved medication or want to understand lawful compounding limits, your preferred treatment form, and your budget. You'll get matched to available paths with source-checked pricing. No account required.

Related guides

• How to Read GLP-1 Clinical Trials
• Placebo-Adjusted Weight Loss Explained
• GLP-1 Lean Mass Loss by Drug
• Compounded GLP-1 Enforcement Tracker
• Best GLP-1 for Cardiovascular Protection
• GLP-1 vs Bariatric Surgery

Primary sources

1. Coskun T, et al. LY3437943, a novel triple glucagon, GIP, and GLP-1 receptor agonist for glycemic control and weight loss: From discovery to clinical proof of concept. Cell Metabolism. 2022;34:1234–1247.e9. https://pubmed.ncbi.nlm.nih.gov/35985340/
2. Urva S, et al. Phase 1b retatrutide trial in type 2 diabetes. The Lancet. 2022;400:1869–1881. https://pubmed.ncbi.nlm.nih.gov/36354040/
3. Rosenstock J, et al. Retatrutide in people with type 2 diabetes. The Lancet. 2023;402:529–544. https://pubmed.ncbi.nlm.nih.gov/37385280/
4. Jastreboff AM, et al. Triple–Hormone-Receptor Agonist Retatrutide for Obesity — A Phase 2 Trial. N Engl J Med. 2023;389:514–526. https://www.nejm.org/doi/full/10.1056/NEJMoa2301972
5. Bajaj HS, et al. TRANSCEND-T2D-1. The Lancet. 2026;407:2402–2413. https://pubmed.ncbi.nlm.nih.gov/42250575/
6. Eli Lilly and Company. TRIUMPH-1 topline results. May 21, 2026. https://investor.lilly.com/news-releases/news-release-details/lillys-triple-agonist-retatrutide-delivered-powerful-weight-loss
7. Eli Lilly and Company. TRIUMPH-2 and TRIUMPH-3 topline results. July 23, 2026. https://investor.lilly.com/news-releases/news-release-details/lillys-triple-agonist-retatrutide-successful-two-additional
8. Eli Lilly and Company. TRIUMPH-4 topline results. December 11, 2025. https://investor.lilly.com/news-releases/news-release-details/lillys-triple-agonist-retatrutide-delivered-weight-loss-average
9. Eli Lilly and Company. TRANSCEND-T2D-1 topline results. March 19, 2026. https://investor.lilly.com/news-releases/news-release-details/lillys-triple-agonist-retatrutide-demonstrated-significant
10. Coskun T, et al. Effects of retatrutide on body composition in people with type 2 diabetes. Lancet Diabetes Endocrinol. 2025;13:674–684. https://pubmed.ncbi.nlm.nih.gov/40609566/
11. US Food and Drug Administration. FDA's Concerns with Unapproved GLP-1 Drugs Used for Weight Loss. https://www.fda.gov/drugs/drug-alerts-and-statements/fdas-concerns-unapproved-glp-1-drugs-used-weight-loss
12. ClinicalTrials.gov. Retatrutide single-patient expanded access — NCT07629401. https://clinicaltrials.gov/study/NCT07629401
13. Zepbound prescribing information. https://pi.lilly.com/us/zepbound-uspi.pdf
14. Wegovy prescribing information. https://www.novo-pi.com/wegovy.pdf
15. Novo Nordisk. Wegovy HD approval and STEP UP results. March 19, 2026. https://www.novonordisk.com/news-and-media/news-and-ir-materials/news-details.html?id=916516
16. Wilding JPH, et al. STEP 1 trial extension. Diabetes Obes Metab. 2022. https://pubmed.ncbi.nlm.nih.gov/35441470/
17. Aronne LJ, et al. SURMOUNT-4. JAMA. 2024. https://pubmed.ncbi.nlm.nih.gov/38078870/
18. ClinicalTrials.gov. TRIUMPH-5 — NCT06662383. https://clinicaltrials.gov/study/NCT06662383
19. ClinicalTrials.gov. TRIUMPH-Outcomes — NCT06383390. https://clinicaltrials.gov/study/NCT06383390
20. ClinicalTrials.gov. Retatrutide maintenance study — NCT06859268. https://clinicaltrials.gov/study/NCT06859268
21. ClinicalTrials.gov. Retatrutide chronic low back pain study — NCT07035093. https://clinicaltrials.gov/study/NCT07035093
22. ClinicalTrials.gov. SYNERGY-Outcomes — NCT07165028. https://clinicaltrials.gov/study/NCT07165028
23. Ro Body pricing. https://ro.co/weight-loss/pricing/
24. Ro GLP-1 Insurance Coverage Checker. https://ro.co/weight-loss/glp1-insurance-checker/

All sources accessed and verified August 7, 2026.

Medical disclaimer: This page reports published clinical trial results for informational purposes. It is not medical advice, and it is not a prediction of what any individual would experience. Retatrutide is an investigational drug that has not been approved by the FDA for any use. Do not start, stop, or change any medication without talking to a licensed healthcare provider. Group averages from clinical trials do not predict individual outcomes.