Retatrutide with cagrilintide
Retatrutide with cagrilintide (grey-market blend)
Written by Aaron CuhaReviewed Sep 2026
Also known as: Reta cagri, Reta/cagri blend, Triple agonist with amylin
In plain English, from Aaron
This is how I would explain it to a friend. The evidence, with the numbers, is further down the page.
Two drugs that are still in testing, mixed in a vial by a research chemical seller. A common one is 12.5 mg retatrutide with 2.5 mg cagrilintide. Neither drug is approved anywhere. No pharmacy makes this. No clinic prescribes it.
What people take it for
- Losing a lot of weight, fast.
- Turning down hunger harder than one drug can.
- Breaking a plateau on a single drug.
What the trials actually showed
Nobody has tested this pair, in people or animals. Each half is good on its own. Retatrutide took off 24.2 percent of body weight at 48 weeks on the 12 mg dose, against 2.1 percent on a dummy shot. At that dose, 83 percent of people lost 15 percent or more. The stomach side effects were dose related and a lower starting dose helped. Heart rate went up with dose. Cagrilintide alone took off 6.0 to 10.8 percent at 26 weeks against 3.0 percent on a dummy shot. The pairing idea has been tested, with a different partner drug. Cagrilintide with semaglutide reached 20.4 percent weight loss at 68 weeks in 3,417 people. The math: 12.5 plus 2.5 is 15 mg, so the vial is 83.3 percent retatrutide and a fixed 5 to 1 split. Mix with 3 mL and every unit mark carries about 42 micrograms of retatrutide and 8 of cagrilintide. Some sellers use 10 plus 2.5, so read your label.
What people report
Reports, not trial results
The good
- Hunger goes very quiet, stronger than either alone.
- Weight comes off fast.
The bad
- Bad nausea and vomiting, more often than on single drug vials, and worst at dose steps.
- A higher resting heart rate, which matches what the retatrutide trial found.
- Fast weight loss with visible muscle loss in people who are not lifting.
- You cannot back one off. The ratio is fixed, and both drugs are stepped up slowly in their own trials for a reason.
Where these come from: Patient forums and seller listings. People talking, using material nobody has tested. The heart rate rise is the one item that also shows up in the real trial.
My bottom line
Both halves are real drugs that are not finished yet. Mixing them at a fixed ratio from an untested vial takes the idea and throws away every safety rail the trials had.
An opinion, not a finding. I am a coach, not a doctor.
Overview
Two unapproved investigational drugs premixed by research chemical vendors, commonly 12.5 mg retatrutide with 2.5 mg cagrilintide in one vial. Neither has finished development, no compounding pharmacy or clinic supplies the pair, and the combination has never been tested in any species. Each component separately has good phase 2 data, which is what makes this look safer than it is.
This is the most aggressive product in the metabolic section and it is worth being precise about why. Both ingredients are real investigational drugs with real trials. Retatrutide, a GIP, GLP-1 and glucagon receptor agonist, produced a 24.2% mean weight change at 48 weeks on 12 mg against 2.1% on placebo in its phase 2 obesity trial. Cagrilintide, a long-acting amylin analogue, produced 6.0% to 10.8% weight reductions across doses at 26 weeks against 3.0% on placebo in its phase 2 trial.
Neither is approved anywhere. Both are still in development. There is no lawful supply of either for human use, which means every vial of this blend comes from a research chemical vendor, unverified, with no pharmacy in the chain. That is a different situation from the compounded GLP-1 products, where at least the active ingredient has an approval somewhere in the world.
The arithmetic on the common 12.5 plus 2.5 mg vial: 15 mg of powder, retatrutide 83.3% and cagrilintide 16.7% by mass, a fixed 5 to 1 ratio. Reconstitute with 3 mL and you have 5 mg/mL total, 4.17 mg/mL of retatrutide and 0.83 mg/mL of cagrilintide. One unit on a 100 unit insulin syringe carries about 42 micrograms of retatrutide and 8 micrograms of cagrilintide. To reach 2 mg of retatrutide you draw about 48 units, which also delivers 0.4 mg of cagrilintide. Some vendors sell 10 plus 2.5, a 4 to 1 ratio, so the split is not standard and the label decides the arithmetic.
The fixed ratio is the specific problem. Retatrutide's trial escalated its dose over months, from 2 mg starting doses up to 12 mg, precisely because the gastrointestinal effects were dose-related and were partially mitigated by a lower start. Cagrilintide has its own escalation. A fixed 5 to 1 blend forces both to escalate together on one schedule, so if you need to hold or reduce one because of nausea, you reduce the other by the same proportion whether or not it was the problem.
There is also a cardiovascular note that belongs on this page. Retatrutide's phase 2 trial reported dose-dependent increases in heart rate that peaked during the trial. Amylin analogues have their own tolerability profile. Nobody has measured what the two do to heart rate together.
Mechanism of action
Retatrutide agonises three receptors: GIP, GLP-1 and glucagon. The glucagon arm is what distinguishes it and is also the arm that raises energy expenditure and can affect heart rate and hepatic glucose output. Cagrilintide is a long-acting amylin analogue acting on satiety signalling through a separate pathway. The combination rationale is that amylin and incretin satiety signals are additive, which has been demonstrated for a different amylin and incretin pair but never for this one.
Human evidence
Both components have phase 2 data separately. The combination has none, and the developed version of this idea used a different incretin.
- This blend: no published study, no registered trial.
- Retatrutide alone: 24.2% mean weight loss at 48 weeks on 12 mg against 2.1% on placebo, with dose-dependent heart rate increases.
- Cagrilintide alone: 6.0% to 10.8% weight reduction across doses at 26 weeks against 3.0% on placebo.
- Amylin plus incretin as a class: cagrilintide with semaglutide reached 20.4% mean weight loss at 68 weeks in a 3,417-participant phase 3 trial, with gastrointestinal events in 79.6% of the combination group.
- Amylin plus triple agonist: never tested in people.
What this does not tell you: The class combination that worked used semaglutide, a GLP-1 only agonist. Retatrutide adds GIP and glucagon receptor agonism, and the glucagon arm carries its own cardiovascular and hepatic effects. Nothing about the semaglutide combination transfers.
What it has been measured to do
Measured in people
Goals Retatrutide with cagrilintide has been measured for in a human being, most people first. Counts come from the study lines on this page and deliberately undercount.
- Losing weight3,755 people · 2 studies
What people using it report
Uncontrolled and self-selected, so it cannot show that anything works. It is still the best guide on this page to what people actually do with Retatrutide with cagrilintide, what they expect, and what goes wrong. The full account, including the negative reports, is below.
34 of the 36 indexed goals have no study of any kind behind Retatrutide with cagrilintide
No trial, no animal work, no cell work on this page reports a result for these. That is an absence of evidence rather than evidence of absence, but it does mean anything you have been told about Retatrutide with cagrilintide and one of these did not come from a study cited here.
Reading the research record
The single most useful comparison for anyone considering this vial is REDEFINE 1. The pharmaceutical version of the same idea, an amylin analogue co-administered with an incretin, has been through a 3,417-person phase 3 trial and reached 20.4% mean weight loss at 68 weeks. It also produced gastrointestinal adverse events in nearly four out of five participants. That is what a developed, dose-escalated, monitored version of this concept looks like, including its cost.
Retatrutide alone reached 24.2% at 48 weeks in phase 2. Adding an amylin analogue to it in a fixed ratio bought from a research vendor is not obviously an improvement on either, and it is definitively a step outside any dataset. Both components are still in development, which means their long-term safety profiles are not established even in the trials, let alone in this configuration.
The evidence, charted
Fig. 1a · evidence scale
4,557people, across 4 human studies cited here
- 2025 · New England Journal of Medicine3,41775%
- 2021 · The Lancet70615%
- 2023 · New England Journal of Medicine3387%
- 2021 · The Lancet962%
One study holds 75% of these participants, so the total is less independent than its size suggests. Counts are the enrollment each human citation on this page states, which includes observational cohorts where nobody was given the compound. Studies still recruiting are excluded, and only studies cited on this page are counted.
Fig. 1b · evidence mix
All 4 citations here are human work.
- Human · given to people4100%
Counted from the citation list on this page, typed as this page types it. It understates any literature larger than the sources we cite, and a review counts once however many studies it covers.
Fig. 2 · evidence over time
Evidence spans 3 distinct years, 2021 to 2025, counted from the citation list on this page.
Fig. 3 · legal status at a glance
US
Not approved
UK
Not approved
AU
Not approved
CA
Not approved
Not approved in any of the four jurisdictions shown. A jurisdiction's classification is a regulatory fact, not a verdict on the science; see Legal status below for the full text and any notes.
Fig. 5 · molecular identity
- Modality
- Blend
- Molecular weight
- Not on file
- Half-life
- Stated in words, not a number
- Sequence length
- None on file
see the exact wording below
Half-life as stated on file: Not defined for the blend. Both components support weekly dosing individually and no pharmacokinetic study of the mixture exists.
No amino acid sequence is on file for Retatrutide with cagrilintide, which is expected: a blend is not built from residues.
Fig. 6 · what is in the vial
83.3%of a 15 mg Retatrutide with cagrilintide vial is Retatrutide
- Retatrutide12.5 mg83.3%
- Cagrilintide2.5 mg16.7%
Label mass from a standard vial, not a dose, and not an assay. The ratio is fixed by the seller, so a draw that hits the amount you want of one component sets the amount of every other component with it. No study has tested this combination in any species.
Key studies & citations
- Human2023
Triple-Hormone-Receptor Agonist Retatrutide for Obesity - A Phase 2 Trial
338 adults with obesity. Least-squares mean weight change at 48 weeks was 8.7% on 1 mg, 17.1% on 4 mg, 22.8% on 8 mg and 24.2% on 12 mg, against 2.1% on placebo. At 12 mg, 83% lost 15% or more of body weight against 2% on placebo. The most common adverse events were gastrointestinal, dose-related, and partially mitigated by a lower 2 mg starting dose. Dose-dependent increases in heart rate were reported. Retatrutide alone.
New England Journal of Medicine - Human2021
Once-weekly cagrilintide for weight management in people with overweight and obesity: a multicentre, randomised, double-blind, placebo-controlled and active-controlled, dose-finding phase 2 trial
706 adults randomised across cagrilintide 0.3 to 4.5 mg, plus liraglutide 3.0 mg and placebo arms. Mean weight reductions at 26 weeks were 6.0% to 10.8% across cagrilintide doses against 3.0% on placebo, with estimated treatment differences of 3.0 to 7.8 percentage points. Cagrilintide alone, in a monotherapy dose-finding trial.
The Lancet - Human2021
Safety, tolerability, pharmacokinetics, and pharmacodynamics of concomitant administration of multiple doses of cagrilintide with semaglutide 2·4 mg for weight management: a randomised, controlled, phase 1b trial
96 people randomised to weekly cagrilintide 0.16 to 4.5 mg or placebo, each in combination with weekly semaglutide 2.4 mg, doses co-escalated over 16 weeks. Of 566 adverse events, 207 were gastrointestinal disorders. Cagrilintide exposure was dose-proportional and did not affect semaglutide exposure. This is the closest thing to combination evidence for an amylin analogue with an incretin, and the incretin was semaglutide rather than retatrutide.
The Lancet - Human2025
Coadministered Cagrilintide and Semaglutide in Adults with Overweight or Obesity
REDEFINE 1, 3,417 participants. Estimated mean weight change from baseline to week 68 was 20.4% on cagrilintide-semaglutide against 3.0% on placebo, a difference of 17.3 percentage points. Gastrointestinal adverse events affected 79.6% of the combination group against 39.9% on placebo. A developed, co-formulated amylin and incretin combination does exist and has been trialled at scale; it is not this one.
New England Journal of Medicine
What users report
Self-reported experiences, not evidence. Nothing below was measured under controlled conditions, and reports like these cannot separate a real effect from placebo, from the training or diet change that accompanied it, or from what the product actually contained. They are here because knowing what people describe, including what goes wrong, is worth reading alongside the studies.
- Very strong appetite suppression, described as stronger than either component alone.
- Severe nausea and vomiting, more often than on single-agent vials, and often at escalation steps.
- Elevated resting heart rate, which matches the dose-dependent increase reported in the retatrutide trial.
- Fast weight loss with visible muscle loss, reported by people not resistance training.
- Difficulty backing off one component, which is the structural complaint about this vial.
Sources: Forums including r/Retatrutide and r/peptides, plus vendor listings. The heart rate observation also appears in the retatrutide phase 2 trial; everything else here is uncontrolled self-report from people using unverified material.
Frequently asked questions
Has this combination been studied?
No, in any species. The related combination that has been studied is cagrilintide with semaglutide, which reached 20.4% mean weight loss at 68 weeks in a 3,417-person phase 3 trial. That used a different incretin.
What is in the vial and in what ratio?
The most common listing is 12.5 mg retatrutide with 2.5 mg cagrilintide, a fixed 5 to 1 ratio, 83.3% retatrutide by mass. Some vendors sell 10 plus 2.5. Reconstituted at 3 mL, one unit carries about 42 micrograms of retatrutide and 8 micrograms of cagrilintide.
Why does the fixed ratio matter here more than usual?
Because both drugs are escalated in their own trials for tolerability reasons. Retatrutide's gastrointestinal effects were dose-related and were partly mitigated by a lower starting dose. A fixed blend means you cannot hold one and continue the other.
Is either drug approved?
Neither, anywhere. Both are investigational, which is why no pharmacy or clinic supplies this and every vial comes from a research chemical vendor.
What about heart rate?
Retatrutide's phase 2 trial reported dose-dependent increases in heart rate. Nobody has measured what happens to heart rate when it is combined with an amylin analogue.