Retatrutide
Weekly weight peptide that burns more rather than just eating less. Milder stomach than sema, strong phase 2 results. Not approved.
What it is
Retatrutide is for the person who wants serious weight loss without the hollow, food-averse feeling of semaglutide or tirzepatide, or who has used those and wants a different lever. It raises how much you burn rather than only cutting how much you eat. It is still in trials, so the dosing is yours to find, and the long-term picture is not in.
Three groups. People who could not tolerate the nausea and food aversion of semaglutide or tirzepatide and want a GLP-1 class drug that leaves them able to eat. People who have already lost on those and stalled, who want the glucagon-driven metabolic push. And larger people who need more total loss than the dual agonists deliver. It is not the choice for someone who wants to feel the appetite door slam shut; by design its appetite suppression is much weaker than semaglutide's (our rough estimate is about a fifth).
The first two weeks are the heaviest: a few days of queasiness after each shot, especially the first one, and a noticeable drop in interest in snacking, though real meals still appeal. From week three the scale moves, usually a steady pound or so a week once you are in your dose. The feel is different from the dual agonists: you run warmer, resting heart rate ticks up a few beats, and you still get hungry at mealtimes, which is fine; that hunger is the deficit working, not a sign the dose is wrong. In the phase 2 trial, people on the top dose lost around a quarter of their body weight over 48 weeks. Liver fat, triglycerides and insulin sensitivity improve along the way. It will not protect muscle for you: eat protein and lift, because losing that fast without resistance training costs lean mass.
Start at 0.5 mg a week if you have never used a GLP-1 and hold at least two to four weeks. Most people settle at 2 to 4 mg a week; larger people run 6 to 10 mg; never past 12 mg. The trick experienced users swear by is splitting the weekly dose in two, roughly every four days: the half-life is about six days, so one big shot gives a heavy onset and a trough by day six, while a split keeps it even and cuts the nausea. Reconstitute at 10 mg per ml so 10 units is 1 mg; a 20 mg vial at 3 mg a week is about seven weeks. Eat enough (this one lets you), keep protein high, and keep a daily bowel movement; constipation is the complaint people ignore until it is a problem. The common mistakes are copying someone else's dose off a forum, jumping from 2 to 6 mg in one step, and stacking it with another GLP-1.
This is a real Lilly drug in phase 3, with a published phase 2 trial showing the largest weight loss of any incretin drug so far, and a mechanism (GLP-1 plus GIP plus glucagon receptor agonism) that explains why: glucagon raises energy expenditure and fat burning, which is the extra you get over tirzepatide. What you do not have is approval, long-term safety data, or any data on the split dosing most people use. The resting heart rate rise is a known trial finding, not a forum rumor. So: strong human evidence for effect, incomplete evidence for safety.
If you want the best-proven option, tirzepatide is approved and close in effect. If you want appetite control more than metabolic push, semaglutide or tirzepatide fit better. If you have a heart rhythm problem or uncontrolled blood pressure, the heart-rate effect makes this the wrong triple agonist; survodutide and mazdutide are the other glucagon-class options, neither approved in the US. And if you want a gentle start, retatrutide at 0.5 mg split is the softest entry on its ladder, though no trial has compared it with semaglutide at 0.25.
What people use it for
Weight loss
Most evidenceThe phase 2 trial in adults with obesity reported average loss of roughly a quarter of body weight at 48 weeks on the highest dose, with no plateau by the end, the biggest result of any incretin drug to date. Phase 3 is under way. For you that means the effect is real and large; what it does not tell you is what happens after year two or at split doses nobody has studied.
Liver fat and metabolic markers
Some evidenceTrial substudies showed large reductions in liver fat, plus improvements in triglycerides, cholesterol and insulin sensitivity, consistent with the glucagon arm pushing the liver to burn fat. Relevant if you have fatty liver or prediabetes, and a reason to recheck labs after three months.
Heart rate and long-term safety
Early daysResting heart rate rose by a few beats per minute in trials, more than with semaglutide, and long-term cardiovascular outcome data do not exist yet. Nausea and vomiting were common but generally milder than the dual agonists at matched loss. This is the gap approval would fill, and it is why going slow matters.
How it works
Where Retatrutide sits in the class
Targets
One molecule, three targets, effects converge.
- Early human trials show strong weight reduction
- Still investigational, in late-stage trials, not yet approved
- Newer and less proven than Semaglutide or Tirzepatide
- The full long-term safety picture is still being established
How people use it
Safety, in brief
Things people sometimes notice
- Queasiness for a few days after each shot, worst after a step up
- Less interest in snacking, with normal meals still appealing
- Running warmer and a resting pulse a few beats higher
- Constipation
The full picture — stop signs and who should talk to a doctor first — is on the dosing guide.
Sources
The labels and studies behind this page. Each link opens the original on PubMed, DailyMed or ClinicalTrials.gov.
- Triple-Hormone-Receptor Agonist Retatrutide for Obesity - A Phase 2 Trial
- Retatrutide in adults with obesity and type 2 diabetes (TRIUMPH-2): a double-blind, parallel-group, randomised, placebo-controlled, phase 3 trial
- Triple hormone receptor agonist retatrutide for metabolic dysfunction-associated steatotic liver disease: a randomized phase 2a trial
- Retatrutide, a GIP, GLP-1 and glucagon receptor agonist, for people with type 2 diabetes: a randomised, double-blind, placebo and active-controlled, parallel-group, phase 2 trial conducted in the USA