The first clear results of retatrutide show in trials after about six months, and the full result after a year and longer. In the phase 2 trial, the 12 mg dose cut body weight by an average of 17.5 percent after 24 weeks and by 24.2 percent after 48 weeks. In the phase 3 trial TRIUMPH-1, the loss after 80 weeks was 25.0 percent. Below you will find these figures point by point, from the first month to two years.
What happens in the first month?
The first month is the time for introducing the dose, not for the full effect. In the phase 2 trial, the group with a 12 mg target dose started at 2 mg a week. The dose was then raised step by step: to 4 mg, 8 mg and finally 12 mg. This is how the trial record on ClinicalTrials.gov describes the scheme.
The lower starting dose had a clear purpose, because the authors write that starting at 2 mg instead of 4 mg partly reduced gastrointestinal complaints. In phase 3, the whole dose-escalation period lasted 16 weeks, followed by 64 weeks on a fixed dose. The result after four weeks therefore says little about the final result.
How much weight can you lose after 3 and 6 months?
The first measurement point described in detail in the phase 2 trial is week 24, roughly six months after the first injection. The trial was published in 2023 in the New England Journal of Medicine. It included 338 adults with obesity, or overweight with a related condition. The table shows the average weight loss at each dose.
| Retatrutide dose | Loss after 24 weeks | Loss after 48 weeks |
|---|---|---|
| 1 mg | 7.2 percent | 8.7 percent |
| 4 mg | 12.9 percent | 17.1 percent |
| 8 mg | 17.3 percent | 22.8 percent |
| 12 mg | 17.5 percent | 24.2 percent |
| Placebo | 1.6 percent | 2.1 percent |
At 8 and 12 mg, the result after six months was already greater than the result after a year at 1 mg. This shows how strongly the pace of weight loss depends on the chosen dose. The trial summary does not report the average loss after 12 weeks separately, so we do not give that figure here.
What result does a full year give?
After 48 weeks, the 12 mg dose gave an average weight loss of 24.2 percent and 8 mg gave 22.8 percent. In the placebo group it was 2.1 percent, and the researchers also counted what share of participants passed successive thresholds.
| Loss after 48 weeks | 4 mg | 8 mg | 12 mg | Placebo |
|---|---|---|---|---|
| at least 5 percent | 92 percent of people | 100 percent of people | 100 percent of people | 27 percent of people |
| at least 10 percent | 75 percent of people | 91 percent of people | 93 percent of people | 9 percent of people |
| at least 15 percent | 60 percent of people | 75 percent of people | 83 percent of people | 2 percent of people |
In the 12 mg group, every participant who reached week 48 had lost at least 5 percent of body weight. More than four in five lost at least 15 percent.
What did TRIUMPH-1 show after 80 weeks?
After 80 weeks the average weight loss was 17.6 percent at 4 mg, 23.7 percent at 9 mg and 25.0 percent at 12 mg. In the placebo group it was 3.9 percent. This is the main result of TRIUMPH-1, published on 29 September 2026 in the New England Journal of Medicine.
The trial included 2339 adults with obesity and without diabetes. The figures include all participants, also those who stopped treatment. The trial also covered people with knee osteoarthritis and with sleep apnoea. In both groups retatrutide reduced complaints more than placebo.
In the subgroup that continued treatment up to 104 weeks, weight loss reached about 30 percent. The Pharmaceutical Journal reported this figure in its coverage of the phase 3 results. After 80 weeks the pace of weight loss is slower than at the start, but weight still keeps falling.
How fast do people with type 2 diabetes lose weight?
People with type 2 diabetes lose weight on retatrutide more slowly than people without diabetes, though still clearly. The same pattern is seen in the trials of semaglutide and tirzepatide. The table collects three trials with different follow-up times.
| Trial | Time | Highest dose | Weight loss | Placebo |
|---|---|---|---|---|
| Phase 2, type 2 diabetes | 36 weeks | 12 mg | 16.94 percent | 3.00 percent |
| TRANSCEND-T2D-1 | 40 weeks | 12 mg | 15.3 percent | 2.6 percent |
| TRIUMPH-2 | 80 weeks | 12 mg | 18.8 percent | 5.1 percent |
TRANSCEND-T2D-1 was published in June 2026 in The Lancet. It included 537 people with recently diagnosed diabetes, on average 2.5 years. TRIUMPH-2 included 1152 people with obesity and diabetes, and its results appeared in September 2026. In both trials glycated haemoglobin, the average blood sugar over recent months, also improved.
What does the pace of weight loss on retatrutide depend on?
The pace depends first of all on the dose, and secondly on whether a person has diabetes. A higher dose gave a greater loss at every measurement point. The difference between 8 and 12 mg was small after 24 weeks and clearer after 48 weeks.
- Dose: 12 mg gave the largest loss after 24, 48 and 80 weeks.
- Diabetes: with type 2 diabetes the loss after 80 weeks was 18.8 percent, without diabetes 25.0 percent.
- Starting dose: starting at 2 mg reduced stomach complaints, which helps reach the target dose.
- Time: most of the effect appears in the first year, then the pace slows.
The most common side effects were gastrointestinal and depended on the dose. In phase 2 they were mostly mild or moderate and appeared more often with a faster start. The researchers also described a rise in heart rate, highest at week 24 and falling in the following months.
How to track progress over the months?
The simplest way is to measure body weight at the same points as the researchers: at the start, after 24 weeks and after 48 weeks. Comparing yourself with the tables only makes sense with a similar measurement rhythm. Next to weight it is worth noting waist circumference, because it changes together with body fat. Which measurements matter is covered in the guide on how to measure peptide results.
Retatrutide acts on three receptors at once: GLP-1, GIP and the glucagon receptor. The mechanism and the first phase 3 results are described in the guide on retatrutide in phase 3. A comparison with semaglutide and tirzepatide is in the guide semaglutide vs tirzepatide vs retatrutide, and the effect on the liver in the guide on retatrutide and fatty liver.
How much does retatrutide cost in the shop?
In the shop, retatrutide comes in three versions from three manufacturers. Retatrutide 20 mg Bio-Peptide costs 200 EUR and is in stock. Retatrutide 20 mg Genheal costs 200 EUR and is available on backorder. Retatrutide 40 mg Nouveaux in a pen costs 350 EUR, so 8.75 EUR per milligram instead of 10 EUR.
How many weeks one vial lasts at successive doses is calculated in the guide on how long a GLP-1 vial lasts. All versions are on the retatrutide page. Retatrutide is not an approved medicine, and the products in the shop are material for laboratory research.
Frequently asked questions
When do the first effects of retatrutide show?
In the phase 2 trial, the 12 mg dose cut body weight by an average of 17.5 percent after 24 weeks. The first weeks are mainly about introducing the dose, usually from 2 mg a week.
How much weight can you lose on retatrutide in a year?
After 48 weeks in the phase 2 trial, the average loss was 24.2 percent at 12 mg and 22.8 percent at 8 mg. In the placebo group it was 2.1 percent.
What result did retatrutide give in TRIUMPH-1?
After 80 weeks the average weight loss was 17.6 percent at 4 mg, 23.7 percent at 9 mg and 25.0 percent at 12 mg, against 3.9 percent on placebo.
Does retatrutide work less well with type 2 diabetes?
It works somewhat less on body weight, though still clearly, because in TRIUMPH-2 the loss after 80 weeks was 18.8 percent at 12 mg, against 25.0 percent in people without diabetes in TRIUMPH-1.
What dose was retatrutide started at in the trials?
In the phase 2 trial mostly at 2 mg a week, and then the dose was raised to 4, 8 and 12 mg. The lower start reduced gastrointestinal complaints compared with starting at 4 mg.
Sources
- Jastreboff AM, Kaplan LM, Frías JP et al. Triple-Hormone-Receptor Agonist Retatrutide for Obesity - A Phase 2 Trial. New England Journal of Medicine, 2023, 389(6): 514-526. https://doi.org/10.1056/NEJMoa2301972
- Jastreboff AM, Kaplan LM, Davies MJ et al. Retatrutide, a Triple Hormone Receptor Agonist, for Treatment of Obesity. New England Journal of Medicine, 2026. https://doi.org/10.1056/NEJMoa2604169
- Bellido V, le Roux CW, Ekinci EI et al. Retatrutide in adults with obesity and type 2 diabetes (TRIUMPH-2). The Lancet, 2026. https://doi.org/10.1016/S0140-6736(26)01861-1
- Bajaj HS, Welch M, Shah P et al. Efficacy and safety of retatrutide in people with type 2 diabetes and inadequate glycaemic control with diet and exercise (TRANSCEND-T2D-1). The Lancet, 2026, 407(10546): 2402-2413. https://doi.org/10.1016/S0140-6736(26)00967-0
- Rosenstock J, Frias J, Jastreboff AM et al. Retatrutide, a GIP, GLP-1 and glucagon receptor agonist, for people with type 2 diabetes: a phase 2 trial conducted in the USA. The Lancet, 2023, 402(10401): 529-544. https://doi.org/10.1016/S0140-6736(23)01053-X
- Giblin K, Kaplan LM, Somers VK et al. Retatrutide for the treatment of obesity, obstructive sleep apnea and knee osteoarthritis: Rationale and design of the TRIUMPH registrational clinical trials. Diabetes, Obesity and Metabolism, 2026, 28(1): 83-93. https://doi.org/10.1111/dom.70209
- ClinicalTrials.gov. LY3437943 in Participants Who Have Obesity or Overweight, NCT04881760. https://clinicaltrials.gov/study/NCT04881760
- The Pharmaceutical Journal. Phase III retatrutide study demonstrates 30% weight loss, 2026. https://pharmaceutical-journal.com/article/news/phase-iii-retatrutide-study-demonstrates-30-weight-loss