Why trial data beats before and after photos
Search for retatrutide results and you will find plenty of before and after photos and anecdotal reviews. None of it tells you much. Retatrutide is not approved anywhere, so anything outside a trial involves an unverified product, and the TGA has already reported Australian products sold as retatrutide that contained no retatrutide at all. A photo cannot tell you what was in the vial.
A randomised trial can. It compares a known dose against placebo in hundreds or thousands of people, measured at fixed timepoints. That is the only retatrutide review worth reading, and it is what this page reports. Nothing here is a prediction for any individual or a suggestion to use the compound.
Retatrutide phase 2 results: weight change at 24 and 48 weeks
The phase 2 obesity trial (Jastreboff et al., New England Journal of Medicine, 2023) randomised 338 adults with obesity, or overweight with a related condition, to weekly retatrutide or placebo for 48 weeks. Average weight change from baseline:
| Group | Week 24 | Week 48 | Lost 15% or more at week 48 |
|---|---|---|---|
| Placebo | 1.6% | 2.1% | 2% |
| 1 mg | 7.2% | 8.7% | not reported here |
| 4 mg (combined) | 12.9% | 17.1% | 60% |
| 8 mg (combined) | 17.3% | 22.8% | 75% |
| 12 mg | 17.5% | 24.2% | 83% |
Two points stand out. Between week 24 and week 48, the higher-dose groups kept losing weight, and the investigators noted that a plateau had not been reached when the study ended. And at 12 mg, every participant lost at least 5%, 93% lost at least 10%, and 83% at least 15%.
How long does retatrutide take to work?
How long does it take for retatrutide to work depends on what you measure. The trials give three answers:
- Weight: the curves separate from placebo early, but the large numbers take months. At 24 weeks, the 12 mg group was at 17.5%; at 48 weeks, 24.2%; at 80 weeks in phase 3, 28.3%.
- Blood glucose: in the phase 2 type 2 diabetes trial the primary endpoint was set at 24 weeks, when HbA1c had fallen by up to 2.02 percentage points on 12 mg.
- Liver fat: most of the reduction was already there at 24 weeks (82.4% on 12 mg) and it held at 48 weeks.
How long does it take for retatrutide to suppress appetite? The published trials did not report appetite as a separate early endpoint, so there is no reliable figure. GLP-1 receptor activity reduces appetite fairly quickly in general, but trial participants were also on a slow escalation that deliberately kept early doses low. Any claim of an exact number of days is not coming from the published data.
Phase 3 results: TRIUMPH and TRANSCEND
The phase 3 programme is much larger and longer. The headline figures reported so far:
| Trial | Population | Length | Reported result |
|---|---|---|---|
| TRIUMPH-1 | 2,339 adults with obesity or overweight, no diabetes | 80 weeks | 19.0% (4 mg), 25.9% (9 mg), 28.3% (12 mg) weight loss |
| TRIUMPH-1 extension | 532 participants with BMI 35 or more | 104 weeks | 30.3% on 12 mg |
| TRIUMPH-4 | 445 adults with obesity and knee osteoarthritis | 68 weeks | 28.7% on 12 mg, 2.1% on placebo |
| TRANSCEND-T2D-1 | 537 adults with type 2 diabetes | 40 weeks | HbA1c down 1.7 to 2.0 points; weight down 11.5% to 16.8% |
| TRIUMPH-2 and TRIUMPH-3 | Obesity with type 2 diabetes, or with cardiovascular disease | 80 weeks | About 21% and 23% at the highest doses |
Most of these are topline figures from Lilly announcements; TRANSCEND-T2D-1 has been published in The Lancet (2026). Our view: quote the 80-week TRIUMPH-1 figure, not the 30.3%. The 104-week number comes from a subgroup of people with higher starting BMI who completed the main trial, so it is not a fair headline.
Liver fat and glycaemic results
The liver fat substudy (Sanyal et al., Nature Medicine, 2024) followed 98 participants with fatty liver disease from the obesity trial. Relative reductions in liver fat at 48 weeks were 51.3% (1 mg), 59.0% (4 mg), 81.7% (8 mg) and 86.0% (12 mg), against 4.6% on placebo. At 24 weeks, 86% of the 12 mg group had reached normal liver fat of under 5%, against none on placebo. This is where the glucagon component is thought to matter most.
In type 2 diabetes, the phase 2 trial (Rosenstock et al., The Lancet, 2023) reported HbA1c reductions at 24 weeks of 1.30% to 2.02% for 4 mg and above, against essentially no change on placebo, and body weight reductions of up to about 16.9% at 36 weeks without a clear plateau. The phase 3 TRANSCEND-T2D-1 results were in the same range. People with diabetes consistently lose less weight on incretin drugs than people without, which explains the smaller numbers in TRIUMPH-2.
Using these results in laboratory research
For a research group, these trial results define what a positive control should look like and which receptor contributions are worth separating. Our explainer on how retatrutide works covers the receptor balance, and the trial side effect data covers tolerability by dose.
For bench work, freeze-dried vials are reconstituted with bacteriostatic water for peptides and measured with U-100 insulin syringes. The retatrutide reconstitution calculator works out concentration per unit for each vial size, and the research library lists the PubMed citations behind this page.
Research use only: Chainwell Peptide sells retatrutide for laboratory research, not for human or veterinary use. The results above are published study findings, not guidance.
Frequently asked questions
How long does retatrutide take to work?
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In the phase 2 obesity trial, weight loss was already substantial at 24 weeks (17.5% on 12 mg) and kept increasing to 24.2% at 48 weeks without a plateau. HbA1c improvements in type 2 diabetes were measured at 24 weeks. Most of the liver fat reduction was present by 24 weeks. These are trial averages, not individual predictions.
How much weight did people lose on retatrutide per week?
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The trials report totals at fixed timepoints rather than weekly rates. As a rough average, the 12 mg group in phase 2 lost 17.5% over the first 24 weeks and a further 6.7 points over the next 24, so the rate slowed over time. Weight loss was not linear, and individual results varied widely around the average.
What are the best retatrutide results reported?
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The highest average reported is 30.3% at 104 weeks on 12 mg in the TRIUMPH-1 extension, but that was a subgroup with a starting BMI of 35 or more who completed the main trial. The fairer headline is the main TRIUMPH-1 result: 28.3% at 80 weeks on 12 mg, reported by Lilly in May 2026.
Are retatrutide before and after photos reliable?
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No. Retatrutide is not approved, so photos online come from people using unverified products, and the TGA has found Australian products labelled retatrutide that contained a different drug. Photos also cannot show dose, duration or diet. Randomised trials with a placebo group are the only reliable source of retatrutide results.
