Retatrutide vs semaglutide: a bigger weight number set against four years of outcome data, with no trial comparing them

Retatrutide's number is bigger. Its phase 2 trial reported 24.2% weight loss at 48 weeks on the highest dose. Semaglutide's pivotal obesity trial reported 14.9% at 68 weeks.

Semaglutide's evidence is deeper. It has been followed in 17,604 people for a mean of about 40 months, where it reduced cardiovascular death, heart attack and stroke by a fifth. Retatrutide has no outcome data of any kind.

The trials are not comparable. 338 people for 48 weeks against 1,961 people for 68 weeks, phase 2 against phase 3.

Nothing has compared them directly. The studies naming both are four rodent experiments, two reviews, a commentary and a network meta-analysis.

One is a medicine you can be prescribed. The other is not available. Retatrutide is investigational, in phase 3, approved nowhere.

The gap looks decisive and is smaller than it appears. Retatrutide's trial was a dose-finding study, which means its job was to find out what the drug does across doses rather than to establish an effect at one. Its curve was still falling at 48 weeks. Semaglutide's trial was the registration study, run to the standard a regulator requires, and its figure is the one that carried into practice.

The only estimates built for comparison are indirect. A 2026 network meta-analysis of 25 trials placed semaglutide 7.2 mg at -14.66% and tirzepatide 15 mg at -17.97%; a second, larger analysis put retatrutide at -22.1%. Across analyses the ordering is consistent, and the confidence intervals overlap.

Weight is a surrogate. What a person actually wants from a weight-loss drug is to live longer and avoid a heart attack, and there is exactly one of these two compounds where that has been measured.

The SELECT trial enrolled 17,604 people with cardiovascular disease and overweight or obesity but without diabetes, and followed them for a mean of 39.8 months. A primary cardiovascular event occurred in 6.5% on semaglutide against 8.0% on placebo, a hazard ratio of 0.80. That is a fifth fewer deaths from cardiovascular causes, heart attacks and strokes, over more than three years.

Retatrutide has nothing of this kind. Not a smaller version, not a preliminary signal: no outcome trial has reported. Its longest published trial ran 48 weeks and measured weight.

So the honest form of the comparison is not 24.2 against 14.9. It is one drug that has been shown to prevent cardiovascular events over years against one that has been shown to produce a large amount of weight loss over a year, with the rest unknown. Those are different kinds of claim, and the second is the more preliminary even though its number is larger.

No trial has given retatrutide and semaglutide to the same participants. The studies in this record that name both are:

One of these was misdescribed in this record's own drafted data: the network meta-analysis of 24,214 participants had been filed as a clinical trial of 214, because the drafter read a space-separated thousands figure as a sample size. It is corrected here and on the tirzepatide comparison, and the underlying script fix is logged.

Semaglutide activates the GLP-1 receptor. That slows gastric emptying, signals fullness and improves insulin secretion, and at 2.4 mg weekly it is the dose approved for weight management.

Retatrutide activates GLP-1, GIP and the glucagon receptor. The glucagon arm is the novel part: it raises energy expenditure and mobilises liver fat, offset by the GLP-1 arm's effect on blood sugar. More receptors is the reason for the larger weight figure and the reason the long-term safety question is more open.

The intermediate case is tirzepatide, which activates two of the three, and is compared with retatrutide on its own page: retatrutide versus tirzepatide.

There is no equivalence between the two scales and no published conversion. A milligram of a triple agonist is not a milligram of a GLP-1 agonist, and retatrutide's figures are the doses a dose-finding study tested rather than a dose anyone settled on.

Both are dominated by gastrointestinal effects during escalation: nausea, vomiting, diarrhoea, constipation. In retatrutide's trial these were the most common adverse events in every dose group.

The asymmetry is in what else is known. Semaglutide's safety profile has been observed in tens of thousands of people over years, including the cardiovascular outcome trial and the diabetes programme before it, which is how less common effects get found. Retatrutide's profile comes from 338 people over 48 weeks, plus pooled analyses of dual and triple agonists as a class that found higher discontinuation than with single-receptor drugs.

The one effect belonging to retatrutide's extra receptor is heart rate, which rose dose-dependently in its phase 2 trial. What that means over years is what its phase 3 programme exists to find out, and it is the single strongest argument for waiting.

Nothing. No trial has enrolled people already taking semaglutide, no published work describes stopping one and starting the other, and no dose conversion has been established. The search demand for this is steady and the literature behind it is empty.

There is also a practical obstacle that the question usually skips: retatrutide is not available. It is in phase 3 and approved nowhere, so there is no legal route to obtain it outside a trial, and material sold under the name comes from outside the regulated supply chain.

Semaglutide is approved and widely prescribed, for type 2 diabetes and for weight management, with a label, a manufacturer and a supply chain.

Retatrutide is investigational. Its phase 3 programme is running, no regulator has approved it, and no approval date has been published. Anything sold under the name today is not the trial drug and has not been shown to contain what its label says.

Each compound's own record carries its full evidence: semaglutide and retatrutide.

Supported: retatrutide produced more weight loss in its trial than semaglutide did in its own; both are dominated by gastrointestinal effects; semaglutide reduces cardiovascular events in people with obesity and established cardiovascular disease; indirect analyses rank retatrutide ahead on weight with overlapping intervals.

Not supported: that retatrutide is better than semaglutide, since better depends on the outcome and only one of them has outcome data; that the 9-point gap in weight figures is a real difference between the drugs; that either is safer; that results transfer to unverified material bought online.

The comparison that will matter is retatrutide's phase 3 programme and, eventually, whether it is followed by an outcome trial of its own. Until then, the drug with the smaller number is the one whose benefits have been measured in the things people care about.

1. Treating 24.2% and 14.9% as a like-for-like difference. Phase 2 against phase 3, 338 people against 1,961, 48 weeks against 68.
2. Ignoring the outcome data. Semaglutide has 17,604 people followed for over three years; retatrutide has none.
3. Assuming a head-to-head trial exists. The studies naming both are rodent experiments and reviews.
4. Planning a switch. Nothing has been studied, no conversion exists, and there is no legal supply of retatrutide.
5. Reading more receptors as strictly better. The glucagon arm is the source of both the extra weight loss and the open safety question.
6. Carrying trial results to grey-market material. The trials used the manufacturer's drug under monitoring.