Cagrilintide vs Retatrutide: What the Trials Show, and What to Know Before Stacking Them

By The RX Index Editorial Team · Last verified October 2026

Cagrilintide vs retatrutide shows a large gap in reported weight loss: 11.8% (2.4 mg) at 68 weeks versus 28.3% (12 mg) at 80 weeks, assuming treatment continued. These were separate Phase 3 trials in adults without diabetes—not a head-to-head test. Neither is FDA-approved or lawful to compound, and we found no published human trial of taking them together.

Three things change how you read those numbers:

• Use the estimates that include people who stopped treatment, and it's 25.0% for retatrutide 12 mg versus 11.5% for cagrilintide 2.4 mg.
• These were two different trials with different lengths. We found no published human trial comparing these drugs head to head.
• Cagrilintide alone is not CagriSema. CagriSema adds semaglutide (the Wegovy ingredient). At 68 weeks, it reached 20.4% regardless of stopping treatment and 22.7% assuming treatment continued.

The bigger story is the trade-off. A larger share stopped retatrutide because of adverse events—health problems reported during a study. Unusual skin sensations were more common than with its placebo, and we found no human trial validating the "reta + cagri" blends sold online. The tables below show the results and the limits of comparing them.

RX Index Decision Verdict: Retatrutide showed larger average weight loss in separate trials; cagrilintide had a lower rate of stopping for adverse events. That is not a head-to-head safety ranking, and neither is an approved pharmacy treatment.

• Best for: understanding what the trials showed and what could change in the next year.
• Not ideal for: choosing a dose, planning a switch, or deciding which research vial to order.
• The factor that matters most: whether you need approved care now or want to explore a legitimate research program.

Cagrilintide vs retatrutide at a glance

In the two Phase 3 trials below, which enrolled adults without diabetes, retatrutide's average weight loss was larger at each dose shown than cagrilintide's. Each result below keeps its trial, length, placebo, and counting method attached, because those change the number.

The trials, side by side (average percent of starting body weight lost)

Both trials enrolled adults with obesity, or with overweight plus a weight-related health problem, and no diabetes. Study doses are listed only to identify the groups; they are not dosing advice. Gaps vs. placebo are our subtraction of the rounded averages within each trial, in percentage points—not a head-to-head effect estimate. A placebo is the inactive comparison treatment. Retatrutide's full trial had 2,339 participants, including 587 assigned placebo. Safety rates use the safety populations shown below. Sources checked October 15, 2026.

Here's the plain read. Retatrutide's reported averages and gaps from its own placebo were larger. Subtracting placebo does not turn separate studies into a head-to-head trial. Cagrilintide had a lower rate of stopping for adverse events, including a lower rate than its own placebo. But its trial was 12 weeks shorter and tested one cagrilintide-only dose. A lower stopping rate does not prove a drug is safer overall.

What those percentages mean in pounds (arithmetic, not a prediction):

Formula: starting weight × percent ÷ 100, rounded to one decimal place. These examples use the treatment-continuation estimates from the separate trials above. Trial averages describe groups. Some people lost much more, some much less, and some stopped early. These are pounds of body weight, not pounds of pure fat.

A quick label check before you trust any headline. Say you see "11.8% versus 28.3%." Attach the missing labels: cagrilintide alone versus retatrutide 12 mg, 68 versus 80 weeks, two separate studies, estimates assuming treatment continued under study rules. Now say a page shows cagrilintide at "22.7%." Check the drug name. In REDEFINE 1, 22.7% belongs to CagriSema, not cagrilintide alone.

Why does one trial have two different results?

Each trial answers two questions. One estimates results for everyone assigned the drug, including people who stopped it. The other estimates what would have happened if people had kept taking it under the study's rules. Both use statistical methods to handle missing results.

Think of a class's average grade. One estimate includes students who dropped the class. Another estimates what the class average would have been if everyone had continued. It isn't just the average of students who stayed. Researchers call each question an estimand, which means the exact question a trial's math is built to answer.

Neither number is a promise for you. The continuation estimates are called trial-product in REDEFINE 1 and efficacy in TRIUMPH-1. The estimates regardless of stopping are called treatment-policy and treatment-regimen, respectively. The rules were not identical, and allowed dose changes still count as treatment. Compare matching types of estimate—not one drug's continuation result with the other drug's result regardless of stopping. Our guide to placebo-adjusted weight loss walks through this in more detail.

Is cagrilintide the same as CagriSema?

No. CagriSema combines cagrilintide and semaglutide as a once-weekly treatment. Its results can't be credited to cagrilintide alone.

The same trial tested all of them, which makes the difference easy to see. Counting everyone, CagriSema averaged 20.4%, semaglutide alone 14.9%, and cagrilintide alone 11.5%. Novo Nordisk says it expects a U.S. FDA decision on CagriSema in the fourth quarter of 2026; that is a company forecast, not an approval. Cagrilintide alone is on a separate, slower track. If CagriSema is what you meant, see CagriSema vs retatrutide.

Choosing care you can start now is a different decision from comparing two drugs that aren't approved yet. The right GLP-1 path isn't the same for everyone: it depends on your state, your insurance and its formulary (the plan's list of covered drugs), whether you want an FDA-approved or compounded medicine, a shot or a pill, and your budget. The RX Index's Find My GLP-1 Path tool asks a few quick questions and shows the paths and providers that fit you. It's free, takes about 2 minutes, and needs no signup. It won't give you access to cagrilintide or retatrutide. Clinical-trial access, and Lilly's limited expanded-access program for retatrutide, are separate from choosing a telehealth provider.

See which GLP-1 path fits you today

How do cagrilintide and retatrutide work?

Cagrilintide copies amylin, a fullness hormone your pancreas releases along with insulin after you eat. It also acts on the closely related calcitonin receptor. Retatrutide is one molecule that switches on three hormone receptors at once: GIP, GLP-1, and glucagon.

A receptor is a spot on a cell that catches a hormone's signal, like a lock waiting for a key. Here's how the two compare:

"Three targets" means one molecule with three jobs, not three drugs mixed in a vial. And "GLP-3" is not the medical name for this drug class. Retatrutide is a GIP/GLP-1/glucagon triple receptor agonist.

More targets doesn't automatically mean better for every person. For the wider amylin picture, see amylin agonists for weight loss.

Which has fewer side effects?

A smaller share stopped cagrilintide for adverse events than stopped retatrutide at its two higher doses. In TRIUMPH-1, nausea and vomiting were more common at the higher retatrutide doses, and unusual skin sensations called dysesthesia were more common than with placebo. Cagrilintide's trial reported a higher injection-site reaction rate. These came from separate trials, so this isn't a head-to-head safety ranking.

"Adverse event" means any health problem reported during a study. The label alone doesn't prove the drug caused it.

Cagrilintide: REDEFINE 1, NEJM Table 3. Retatrutide: Lilly Medical's detailed TRIUMPH-1 tables, citing the September 29, 2026 NEJM paper. A dash means the cited table does not separately report that outcome; it does not mean no events occurred. Safety populations: 302 and 705 for cagrilintide and its placebo; 584, 583, 582, and 586 for retatrutide 4, 9, and 12 mg and its placebo. Retatrutide's adverse-event discontinuation row excludes deaths. Serious events are reported events, not proof the drug caused them. Checked October 15, 2026.

A few things worth knowing:

• Stopping the drug is not the same as leaving the study. The two stopping rows count people who stopped the medicine because of an adverse event.
• Dysesthesia was mostly mild to moderate, and Lilly says most cases cleared up during treatment.
• The trial numbers came with careful, gradual dose increases and clinical monitoring. The studies also allowed dose changes under their rules. A research vial from a website does not establish the same product quality, monitoring, or safeguards.

If a side effect is bothering you on any weight-loss medicine, talk to the clinician who prescribed it. For the full trial-by-trial picture, see retatrutide side effects.

If you've used a product sold as retatrutide or cagrilintide and are worried about a reaction or the amount you took, call U.S. Poison Control at 1-800-222-1222. Do not wait to feel very unwell. Call 911 if someone collapses, has a seizure, has trouble breathing, or cannot be awakened.

Can you take cagrilintide and retatrutide together?

We found no published human trial testing cagrilintide with retatrutide, so there is no established human safety profile or dosing plan for the pair. The direct combination study we found tested rats. A "stack" dose online is not backed by human trial evidence for this combination.

Here's what's real, and what isn't. The claims below are examples, not quotes from patients or trial researchers.

Rounding note: REDEFINE 1 reports a model-estimated CagriSema–placebo difference of 17.3 percentage points. Subtracting the displayed rounded averages gives 17.4. The arithmetic above is an illustration, not a formal test of how the drugs interact.

We can't give you a safe stack dose because no human regimen for this pair has been established. What does exist: registered trials that test other amylin treatment combinations, with doctors watching. You can search them by drug name on ClinicalTrials.gov and contact the listed study site. A listing doesn't guarantee a nearby site is enrolling or that you'll qualify. Ask the study team about eligibility, whether you could receive placebo, required visits, travel, and any costs before agreeing. Our amylin guide lists the studies we've tracked.

Say you're on Zepbound, you've lost 45 pounds, and the scale hasn't moved in six weeks. A forum post says to "add a little reta or cagri." The honest first step is your prescriber, not an unapproved add-on. Bring one question: "What should we review before deciding my current treatment has stopped working?" Our guide to what to try after Zepbound stalls covers the approved options.

If you've already used one of these products, tell a licensed clinician exactly what you took and when.

Is it legal to buy "research" cagrilintide or retatrutide?

Not as a lawful shortcut to patient treatment in the U.S. Neither drug is FDA-approved, and the FDA says neither can be used in compounding under federal law. A genuine laboratory-research sale is a different question from selling a drug for people to take; a "research use only" label does not make that human-use sale lawful.

The FDA's current page on unapproved GLP-1 drugs (content current October 1, 2026) says plainly that retatrutide and cagrilintide are not parts of any FDA-approved drug and have not been found safe and effective for any condition. It urges people not to buy products labeled "research purposes" or "not for human consumption," calling them of unknown quality and possibly harmful.

That means there's no lawful compounding shortcut for these two drugs. Compounding means making or changing a medicine to meet a medical need. Even when it's allowed for other drugs, compounded medicines are not FDA-approved, and the FDA doesn't review them for safety, effectiveness, or quality before they're marketed. Clinical trials and authorized expanded access are different from commercial compounding.

What regulators and the manufacturer have documented:

• FDA warning: In its December 10, 2024 letter to Summit Research Peptides, the FDA addressed retatrutide and cagrilintide sold for human use despite research-only labels. It said the products violated federal drug law.
• August 12, 2026: Lilly announced six new lawsuits against U.S. sellers. That is a company enforcement announcement, not a finding that every allegation has been proved in court.

Red flags on any seller:

• "Research use only" next to dosing tips
• No prescription and no licensed prescriber
• No named, licensed pharmacy
• Pre-mixed "reta + cagri" blends
• A promised weight-loss percentage

More on spotting fakes: how to avoid fake GLP-1 medications online and our compounded GLP-1 enforcement tracker.

When could either one be available?

Lilly plans to submit its retatrutide application to the FDA in the first quarter of 2027. Novo Nordisk lists 2028 as its expected launch for cagrilintide alone. Both are company plans, not approvals, and neither gives you a confirmed date to fill a prescription.

Each step is its own gate: applied, reviewed, approved, launched, stocked in pharmacies, then covered (or not) by insurance. Submitting an application is not approval or a date when you can fill a prescription. Current authorized access to retatrutide is through clinical trials or Lilly's limited expanded-access program, which a treating doctor must request.

Expanded access is not a general sign-up program. Lilly considers adults whose BMI (body mass index, a measure based on height and weight) remains at least 35 despite taking and tolerating the highest available dose of weight-management treatment. They must also have at least two serious or life-threatening obesity-related complications under standard care and be unable to join a suitable trial. All standard options, including weight-loss surgery, must have been discussed. A detailed medical and regulatory review is still required. Lilly says it supplies the drug at no cost; that does not mean all related medical care is free. Start with your treating doctor. More on that in retatrutide availability.

Neither has a verified commercial prescription price in the U.S. yet. A forecast, research-vial listing, or research-program cost is not the price of an approved prescription.

What's the closest legal option today?

If retatrutide's results are what draw you, tirzepatide (Zepbound) is the closest FDA-approved option by receptor targets: it acts on two of retatrutide's three targets and is approved for weight management. That does not mean it produces the same results. No amylin-based drug is FDA-approved for weight loss as of this check. A licensed clinician decides what fits your health history.

Retatrutide and tirzepatide are being compared head to head in TRIUMPH-5. We found no published results from that trial. Even a direct trial will compare group averages, not predict which drug works better for you. What we can say is that tirzepatide is an approved option to discuss now.

One option we recommend for the approved route: Ro, for adults who want an online clinician and insurance help. The options discussed here are FDA-approved medicines, not compounded versions. Ro's published program does not offer retatrutide or cagrilintide. And if all you want is the lowest cash price, Ro says its medication prices match LillyDirect, NovoCare, and TrumpRx, so the membership is the extra you'd pay. Already have a prescriber? Ask about filling through LillyDirect or your pharmacy rather than paying for another care membership.

What Ro's membership gets you is a licensed clinician, help with dose changes and side effects, and an insurance concierge that checks your coverage and handles prior-authorization paperwork (think of prior authorization as a permission slip from your insurer). Ro says Medicaid patients are not eligible for its treatment program. With Medicare, Medicaid, or another government plan, start with your plan and treating clinician rather than assuming this cash-pay example is your best path.

Here are the membership and medication charges for Zepbound KwikPen on Ro, paying cash, checked against Ro's pricing and Lilly's offer terms on October 15, 2026. A drug supply is 28 days, not a calendar month. These are subtotals before any extra supplies, tests, or fees—not a guaranteed all-in receipt:

Get started for $39, then as low as $74/month with the annual plan paid upfront. Medication is billed separately. The 5 mg supply is $399. Ro advertises the $39 intro first, followed by the selected plan; confirm the annual plan's billing date before paying. The table is not a first-year total; membership and pharmacy billing dates can differ. The 2.5 mg dose is a starting dose, not an approved maintenance dose. Prices change; confirm before you pay.

The $449 price has a catch: Lilly's terms require a refill purchase within 45 days after delivery or receipt of the previous supply to keep that offer. Without it, the listed regular price is $499 for 7.5 mg or $699 for 10, 12.5, or 15 mg. At those three higher doses, a $149 membership charge plus a $699 supply would total $848 before extras, not $598. This is a purchase deadline for the offer—not advice to change when you take your medicine. Manufacturer terms.

What can cost extra: LillyDirect says pen needles must be purchased. Ro includes provider-ordered testing and up to 24 medical consults a year under its terms, but extra consults cost $15 each and additional tests have separate fees. Confirm supplies, shipping, taxes, and other pharmacy charges before paying. We did not complete checkout, so any unconfirmed fee is unknown—not zero.

Before prepaying: Ro's terms say paid membership fees are nonrefundable and renew automatically at the price and frequency agreed at checkout. Cancel at least 48 hours before renewal; already-paid access continues to the end of that billing period. A delay in getting medicine does not automatically stop membership charges. Ro separately says it refunds the initial purchase if no medication is prescribed.

Before paying for a membership, Ro's free insurance check can report coverage for Ozempic pen, Wegovy pen, and Zepbound single-dose pen. It does not check Zepbound KwikPen or the oral medicines, and a coverage report does not guarantee a prescription or insurer approval. The pen coverage check and the cash-pay KwikPen examples above are different options.

Check your Zepbound coverage with Ro

Want to compare more than one provider, or are you weighing FDA-approved versus compounded options? Find My GLP-1 Path shows the paths and providers that fit your goals, budget, insurance, and situation. Compounded medicines are not FDA-approved, and they are not cagrilintide or retatrutide. Our compounded vs name-brand guide explains the difference.

What we actually verified

Last verified October 2026. On October 15, 2026, we checked the sources below and recalculated the examples rather than trusting headlines. Trial findings, company plans, and provider terms are labeled for what they are.

• Trial data: REDEFINE 1's published methods, Figure 1, and Table 3, including visual checks of the figure and table; and Lilly Medical's detailed TRIUMPH-1 efficacy and safety tables, which cite the September 29, 2026 NEJM paper. We couldn't open that NEJM full text directly. Lilly Medical's table differs slightly from the May 21 release (for example, 11.2% instead of 11.3% stopping for adverse events at 12 mg); we used the detailed table and identify its source. Its displayed review date predates the paper it cites, so we could not independently resolve that date inconsistency.
• Legal status: the FDA's page on unapproved GLP-1 drugs, content current October 1, 2026.
• Company plans: Lilly's September 29, 2026 release (filing plan) and Novo Nordisk's September 21, 2026 investor presentation (launch expectations). These are company-stated, not guarantees.
• Combination evidence: the published abstract of the September 2026 rat study. We didn't read the paywalled full text.
• Research access and enforcement: Lilly's expanded-access criteria and sponsor pages for TRIUMPH-5 and ENLIGHTEN-6; the FDA's December 2024 warning letter; and Lilly's August 2026 lawsuit announcement. Local enrollment and individual access were not tested.
• Prices and terms: Ro's public pricing, Zepbound, insurance-checker, insurance, and membership-terms pages; plus Lilly's supply prices and offer terms, checked October 15, 2026. These are provider- and manufacturer-stated; we didn't complete checkout or submit an insurance check.
• What we couldn't confirm: a published human trial of the combination or a human head-to-head trial of these two drugs; live enrollment at a specific site; future commercial prices or insurance coverage for either drug; or an individual Ro checkout total. We did not test the Find My GLP-1 Path questionnaire from start to finish.

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

We don't give investigational drugs a score. This page uses the RX Index Decision Verdict; see how we evaluate.

Frequently asked questions

Should I add retatrutide or cagrilintide to my Mounjaro or Zepbound?

Do not add either on your own. Zepbound's prescribing information does not recommend using it with another GLP-1 receptor agonist; retatrutide activates that receptor. Neither experimental drug is lawful to compound, and evidence for other amylin add-on treatments does not establish a safe cagrilintide–tirzepatide or retatrutide–tirzepatide regimen. A stall on your current medicine is a conversation for your prescriber, who can review your treatment and approved options.

Is there human evidence for taking cagrilintide and retatrutide together?

We found no published human trial as of October 15, 2026. The direct combination study we found tested obese male rats and reported more weight loss than either drug alone. Rat results can't tell you a safe human dose.

Which is better: CagriSema or retatrutide?

In separate trials, retatrutide 12 mg averaged 28.3% at 80 weeks and CagriSema 22.7% at 68 weeks in analyses assuming treatment continued. Those results do not establish a head-to-head winner. Novo expects a U.S. CagriSema decision in Q4 2026; that is not a guaranteed approval. Our CagriSema vs retatrutide guide compares them in full.

Is cagrilintide a GLP-1 drug?

No. Cagrilintide copies amylin, a fullness hormone, and acts on amylin and calcitonin receptors. CagriSema adds semaglutide, which is a GLP-1 drug.

Is cagrilintide FDA-approved?

No. Its RENEW Phase 3 program is ongoing, and Novo Nordisk lists 2028 as an expected launch—not an approved launch date. The FDA says cagrilintide can't be used in compounding.

When will retatrutide be approved?

There's no confirmed approval date. Lilly plans to apply in the first quarter of 2027; applying does not guarantee approval or launch. Current authorized access is through clinical trials or the limited expanded-access program that a treating doctor must request.

Is "research use only" retatrutide legal?

A "research use only" label does not make a product lawful to sell as human treatment. The FDA has warned sellers using that wording while marketing unapproved drugs to consumers with dosing instructions. It urges consumers not to buy those products because their quality is unknown; genuine laboratory research is a different use.

Which has fewer side effects?

A smaller share stopped cagrilintide for adverse events (2.6%) than retatrutide 12 mg (11.2%) in the separate trials above. Their placebo rates were 3.5% and 4.6%, respectively. Retatrutide had more nausea and vomiting at higher doses within its trial, while cagrilintide's trial reported more injection-site reactions. These figures do not prove which drug is safer for you.

Do these results apply if I have type 2 diabetes?

Not directly. Both trials in our main table excluded diabetes. In TRIUMPH-2, adults with type 2 diabetes assigned retatrutide 12 mg had an estimated 20.8% weight loss at 80 weeks assuming treatment continued, versus 4.0% with placebo. That is separate diabetes-specific evidence, not a result to swap into the main table.

Are cagrilintide or retatrutide pills?

No. Both were tested as weekly shots under the skin. Results from those trials don't apply to any pill, drop, or seller-made version.

What will they cost, and will insurance cover them?

Neither has a verified U.S. commercial prescription price or routine coverage for an approved product. A research seller's price is not the price of an approved prescription, and any future coverage will depend on the product, its approved use, and your plan. Trial or expanded-access costs are separate questions.

Does retatrutide or cagrilintide protect muscle better?

We found no human head-to-head evidence showing which of these two protects muscle better. A retatrutide body-composition substudy in adults with type 2 diabetes reported fat loss and some lean-mass loss; it did not compare cagrilintide. Lean mass is not a measure of muscle alone. See our lean mass by drug research.

Sources

• Garvey WT, et al. Coadministered Cagrilintide and Semaglutide in Adults with Overweight or Obesity (REDEFINE 1). NEJM, 2025. Full text. Rechecked October 15, 2026 (prior source check: October 14, 2026).
• Lilly Medical. Results of retatrutide from TRIUMPH-1 (Tables 1 and 3; cites Jastreboff AM, et al., NEJM, September 29, 2026, doi 10.1056/NEJMoa2604169). Lilly Medical. Checked October 15, 2026.
• Eli Lilly. TRIUMPH-1 topline release, May 21, 2026. Company release. Rechecked October 15, 2026 (prior source check: October 14, 2026).
• Eli Lilly. TRIUMPH-2 results and filing plan, September 29, 2026. Lilly. Checked October 15, 2026.
• Novo Nordisk. Capital Markets Day obesity presentation, September 21, 2026. Novo Nordisk. Checked October 15, 2026.
• U.S. FDA. FDA's Concerns with Unapproved GLP-1 Drugs Used for Weight Loss, content current October 1, 2026. FDA. Checked October 15, 2026.
• Petersen J, et al. Cagrilintide and retatrutide combination therapy enhances weight loss and metabolic outcomes in obese male rats. Nature Metabolism, September 15, 2026. Nature. Abstract checked October 15, 2026.
• U.S. FDA. Warning letter to Summit Research Peptides, December 10, 2024. FDA. Checked October 15, 2026.
• Eli Lilly. Retatrutide enforcement announcement, August 12, 2026. Company release. Checked October 15, 2026.
• Eli Lilly. TRIUMPH-5, registry identifier NCT06662383, and ENLIGHTEN-6, NCT07392190. Sponsor pages checked October 15, 2026; individual-site enrollment not confirmed.
• Lilly Medical. Expanded access to retatrutide, referring to NCT07629401. Checked October 15, 2026.
• Coskun T, et al. Effects of retatrutide on body composition in people with type 2 diabetes. Lancet Diabetes & Endocrinology, 2025. Published abstract. Checked October 15, 2026.
• Eli Lilly. Zepbound prescribing information, manufacturer offer terms, and LillyDirect Zepbound details. Checked October 15, 2026.
• National Capital Poison Center. Poison help and emergency guidance. Checked October 15, 2026.
• Ro. Pricing, Zepbound, terms of use, insurance, and free insurance checker. Checked October 15, 2026; checkout and a personal insurance report not completed.

Still not sure which GLP-1 path fits you? Take The RX Index's free Find My GLP-1 Path quiz — about 2 minutes, no signup.