How much weight can you actually lose on retatrutide

Key takeaways

• In its Phase 2 trial, the highest retatrutide dose (12 mg) cut body weight by about 24.2 percent at 48 weeks, versus 2.1 percent on placebo .
• A 2026 Phase 3 readout (TRIUMPH-1) went further: the 12 mg dose averaged roughly 28 percent at 80 weeks among people who stayed on it, and about 30 percent at two years in a higher-BMI subgroup .
• For comparison, in their own trials semaglutide (Wegovy) averaged about 14.9 percent at 68 weeks and tirzepatide (Zepbound) up to about 22.5 percent at 72 weeks . No trial has compared the three head to head.
• The number climbs with the dose. The same Phase 2 trial saw about 8.7 percent at 1 mg, 17.1 percent at 4 mg, and 22.8 percent at 8 mg . Higher doses also meant more side effects, and about 11 percent of people stopped the 12 mg arm in Phase 3 .
• Retatrutide is still investigational. It is not FDA approved, an approval is not expected before 2027, and these are trial averages, not a prescription you can fill .

The actual numbers, side by side

Here are the headline figures from each drug's own pivotal trials. Read the comparison loosely, not literally: these are separate studies of different lengths in different groups of people, and nobody has run retatrutide head to head against the others.

Why retatrutide reaches a higher number

The short answer is that it pulls more levers. Semaglutide works on one hormone receptor (GLP-1). Tirzepatide works on two (GLP-1 and GIP). Retatrutide works on three, adding glucagon .

GLP-1 and GIP mostly turn appetite down. The glucagon arm is the twist, because glucagon also nudges the body to spend a bit more energy, not just eat less. Stack the three and you get a steeper average drop on the scale.

The cleanest way to see the dose effect is inside one trial, where it is the same people over the same 48 weeks. In Phase 2, the average loss climbed dose by dose, all the way to 24.2 percent on 12 mg .

A trial average is not your number

An average hides the spread. Behind that 24 percent are people who lost far more and people who lost much less. The headline is a midpoint, not a forecast for you.

The number also depends on how you count. The Phase 3 figure for the top dose at 80 weeks is reported as about 28 percent if you count the people who stayed on the drug, or about 25 percent if you count everyone who started, including those who stopped . Both are honest. They answer slightly different questions.

It is not approved yet, and that matters

The excitement skips over one fact. As of mid-2026, retatrutide is investigational. It is not approved by the FDA or any other regulator, and in Lilly's own words it is legally available only to people in its clinical trials . A New Drug Application was expected in late 2026, with approval not anticipated before 2027 .

That gap is why retatrutide already turns up in gray-market research-chemical channels, sold without a trial's medical supervision, slow dose titration, or quality control. The trial numbers came with all three. A vial bought online does not, and the dose ladder above is what the studies used, not a protocol to copy.

The honest bottom line

So, how much can you actually lose on retatrutide. In the trials, a lot: roughly a quarter of body weight at one year, and close to a third at two years on the top dose. It is the most weight loss any obesity drug has shown in a trial so far, attached to a drug you cannot yet be prescribed.

Whether you would see those numbers is a different question, and the honest answer is that no one can promise it. The averages are real. They are also averages, on a drug still working its way through Phase 3.

For research and educational purposes only. Not medical advice.

pepSmart has not commissioned independent clinical review of this article.

More on how we write and source these pieces: Editorial process and contributor disclosure and Sourcing posture.

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Sources: 6 entries, primary canon (the NEJM trials and ClinicalTrials.gov) plus reputable secondary sources with inline acknowledgment (Lilly's topline release and the Pharmaceutical Journal), last reviewed 2026-06-04.

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