Retatrutide TRIUMPH-2 Results: What the Full Type 2 Diabetes Data Actually Shows

The full retatrutide TRIUMPH-2 results were published in The Lancet on 29 September 2026 and presented at the European Association for the Study of Diabetes (EASD) meeting in Milan. TRIUMPH-2 is Eli Lilly’s Phase 3 trial in adults living with obesity or overweight and type 2 diabetes.

If the headline number sounds familiar, it should. Lilly first announced the 20.8% average weight loss figure in July, and we covered those topline results at the time. What is new is the detail behind it. The clearest new finding is that on the highest dose, around half of people lost at least a fifth of their starting weight and around one in three lost at least a quarter. Roughly one in three lost less than 15%.

Here is what the retatrutide TRIUMPH-2 results actually show, and what they do and do not mean for anyone in the UK.

What was already known, and what is new

It is worth separating the two clearly, because some coverage this week is presenting July’s numbers as if they were brand new.

Already announced by Lilly in July 2026:

• Average weight loss at 80 weeks of 12.7% (4 mg), 19.1% (9 mg) and 20.8% (12 mg), compared with 4.0% on placebo.
• Average HbA1c (long-term blood sugar) reductions of 1.4, 1.6 and 1.5 percentage points on the three doses, compared with 0.2 on placebo.
• The most common side effects and the rates of people stopping treatment because of side effects.

New with the full results and Lancet publication:

• How results were spread out: about half of people on 12 mg lost at least 20%, and about one in three lost at least 25%.
• A more cautious average that includes everyone who started the trial, even people who stopped: 18.8% on 12 mg.
• How many people no longer counted as having obesity by the end, and results for people who started with a BMI of 35 or more.
• How many people got their blood sugar below diabetes and normal-range levels, plus changes in blood pressure, cholesterol and waist size.
• More safety detail, including low blood pressure and deaths during the trial.
• The peer-reviewed paper itself, with the full details of who took part.

Who was in the TRIUMPH-2 trial?

This matters more than any single percentage, because results apply best to people like those studied.

• 1,152 adults with type 2 diabetes and a BMI of 27 or more, at 92 sites in eight countries: the United States, India, Australia, Mexico, Spain, Romania, Argentina and Brazil. There were no UK sites.
• Their HbA1c was between 6.5% and 10.5%, and they were managing diabetes with diet and exercise or up to three diabetes tablets. People using insulin were not part of this group, and 92% were taking at least one diabetes tablet.
• The average participant was 55 years old, and 48% were women. That makes this trial more relevant than most to many of our readers.
• Average starting weight was 106.4 kg (about 16 stone 11 lb), average BMI was 38.2 and average HbA1c was 7.7%.

Each person was randomly given one of three doses of retatrutide (4 mg, 9 mg or 12 mg) or a dummy placebo injection, once a week for 80 weeks (just over 18 months). Everyone started on 2 mg and stepped up every four weeks. Neither they nor their doctors knew who was on what.

How much weight did people lose?

You will see two different averages quoted. Both are genuine. They just answer slightly different questions.

20.8% is Lilly’s headline figure. It estimates the weight people would have lost if everyone had stayed on their injections for the full 80 weeks (the “efficacy estimand”):

• 4 mg: 12.7% (13.5 kg, about 2 stone 2 lb)
• 9 mg: 19.1% (20.6 kg, about 3 stone 3 lb)
• 12 mg: 20.8% (22.5 kg, about 3 stone 8 lb)
• Placebo: 4.0% (4.2 kg, about 9 lb)

18.8% is the main figure in the Lancet paper. It includes everyone who started the trial, including people who stopped their injections along the way (the “treatment-regimen estimand”). That is closer to real life, where not everyone stays on treatment:

• 4 mg: 11.9%
• 9 mg: 16.8%
• 12 mg: 18.8%
• Placebo: 5.1%

About 84% of participants completed their treatment. So when you see “20.8%”, read it as the “if you stay on it” figure.

Around half lost a fifth of their weight, but not everyone did

An average is not a promise. The new figures show how results were spread out on the 12 mg dose, for people who stayed on treatment:

• About half (52.0%) lost at least 20% of their starting weight. For someone starting at 16 stone, that is at least 3 stone 3 lb.
• About one in three (34.9%) lost at least 25%, a quarter of their body weight.
• About two in three (67.0%) lost at least 15%.

The other side matters just as much. Roughly one in three people on the highest dose lost less than 15%, and about half lost less than 20%. On placebo, 6.4% lost at least 15%.

In other words, losing around a fifth of your body weight was common on the highest dose, but it was not guaranteed. Nobody can know in advance which group they would fall into.

Two more new figures for the 12 mg dose:

• 59.5% no longer met the BMI definition of obesity by the end. BMI is a blunt measure, but it gives a sense of scale.
• People who started with a BMI of 35 or more lost 23.4% on average (about 27.6 kg, or 4 stone 5 lb).

Why is 20.8% lower than the 28.3% from TRIUMPH-1?

Earlier this year, TRIUMPH-1 reported 28.3% average weight loss on 12 mg over 80 weeks, also an “if people stayed on it” figure. That trial studied people with obesity who did not have type 2 diabetes.

People with type 2 diabetes consistently lose less weight on these medicines than people without it. The same pattern appeared with tirzepatide (Mounjaro): in Lilly’s SURMOUNT-2 trial in people with obesity and type 2 diabetes, average weight loss at 72 weeks was 12.8% on 10 mg and 14.7% on 15 mg, counting everyone in the same way as retatrutide’s 18.8% (Lancet, 2023).

That comparison is interesting, but it is not a head-to-head result. The trials ran for different lengths of time with different participants. No completed trial has yet compared retatrutide and Mounjaro directly. Our retatrutide vs Mounjaro explainer goes into why cross-trial comparisons need care.

Blood sugar, blood pressure and cholesterol

Blood sugar improved a lot. HbA1c, the test used to track diabetes over about three months, started at an average of 7.7%. It fell by 1.4 to 1.6 percentage points across the three doses, compared with 0.2 on placebo.

• 79.0% of people on 12 mg got their HbA1c down to 6.5% or lower, the level used to diagnose diabetes. On placebo it was 26.3%.
• About four in ten (39.3% on 12 mg, 40.0% on 9 mg) got below 5.7%, the normal non-diabetic range. On placebo it was 4.4%.

That last figure is striking, but Lilly says it was not statistically tested as strictly as the main results, so treat it as encouraging rather than definitive. It does not mean diabetes was “cured”: these people were still on treatment, and the trial does not show what happens if retatrutide is stopped.

Heart-health risk factors also moved in the right direction. On 12 mg, on average:

• Waist size fell by 16.9 cm (6.7 inches)
• The top blood pressure number fell by 10.8 mmHg
• Triglycerides (a blood fat) fell by 39.5% and “bad” non-HDL cholesterol by 19.6%
• A marker of inflammation (hsCRP) fell by 58.3%

These are improvements in risk factors. They are not evidence yet that retatrutide prevents heart attacks or strokes. That is being tested separately in a large outcomes trial, TRIUMPH-Outcomes, which has not yet reported.

Side effects and safety

As with Mounjaro and Wegovy, the most common side effects were digestive, and they were more common at higher doses:

• Diarrhoea: 27% (4 mg), 34% (9 mg), 34% (12 mg) vs 13% on placebo
• Nausea: 14%, 21%, 28% vs 8%
• Constipation: 14%, 16%, 17% vs 9%
• Vomiting: 6%, 10%, 16% vs 4%
• Reduced appetite: 6%, 12%, 17% vs 5%

Lilly says these were generally mild to moderate and mostly settled during treatment.

Other findings worth knowing about:

• Dysesthesia, an altered skin sensation such as tingling or unusual sensitivity, affected 4%, 6% and 7% of people on retatrutide compared with 1% on placebo. It has appeared across the retatrutide Phase 3 programme.
• Low blood pressure (hypotension) was more frequent with retatrutide: 1%, 5% and 6% compared with under 1% on placebo. This is a new detail from the published paper.
• Stopping treatment because of side effects (or death) happened in 4% (4 mg), 12% (9 mg) and 8% (12 mg), compared with 5% on placebo. In this trial, the middle dose had the highest drop-out rate for side effects.
• Deaths: seven participants died during the trial: two on 4 mg, three on 9 mg, one on 12 mg and one on placebo. The investigators judged all of them to be unrelated to the study treatment.

Figures for heart rate, pancreatitis, gallbladder problems, low blood sugar (hypoglycaemia) and overall serious side effects were not included in the Lancet summary or Lilly’s results release reviewed for this article. Earlier retatrutide research reported increases in heart rate.

What the trial cannot tell us

• It is funded and co-authored by Eli Lilly. That is normal for Phase 3 trials and the paper is peer-reviewed, but independent analysis of the full data will take time.
• It compared retatrutide with placebo, not with Mounjaro or Wegovy.
• It lasted 80 weeks. It does not show what happens over many years, or after stopping treatment.
• It studied a specific group: adults with type 2 diabetes managed without insulin. The results should not be applied to people without diabetes (that was TRIUMPH-1) or to people using insulin.
• It included no UK sites. 58% of participants were White.
• Some of the most eye-catching numbers are secondary results. They include the responder rates and the normal HbA1c figure, which was not controlled for statistical error.

Can you get retatrutide in the UK?

No. Retatrutide is still an investigational medicine. It is not authorised in the UK and has not been approved by any medicines regulator. In July 2026 the MHRA warned that it “has not been authorised for use in the UK”, and that anyone selling it is doing so illegally.

Lilly says its Phase 3 programme now provides the clinical data needed to support regulatory submissions. The next steps before anyone in the UK could legitimately be prescribed it are:

• Regulatory submission and review. Lilly says it plans to apply to the US FDA in the first quarter of 2027. It has not announced a date for a UK application. The MHRA would need to assess the full evidence and grant a UK marketing authorisation.
• Private prescribing could only begin after UK authorisation.
• NHS access would additionally need a NICE appraisal and local commissioning decisions.

There is no official UK launch date. Any date you see quoted online is a guess. Our Retatrutide UK guide tracks the regulatory position as it develops.

Products sold online as “retatrutide” are not Lilly’s medicine and have not been through any safety or quality checks. Strong trial results do not make them safer. In June 2026, health authorities in Victoria, Australia reported six cases of acute liver injury since January in people who had used unapproved products labelled as retatrutide. They said a contaminant in the products may be responsible.

If you have type 2 diabetes and are currently on Mounjaro, Wegovy or another prescribed treatment, these results are not a reason to stop or change it. Treatments that are licensed in the UK now have established prescribing information and safety monitoring. Any decision about your treatment should be made with your prescriber.

The bottom line

The full retatrutide TRIUMPH-2 results confirm what Lilly announced in July and add useful detail. In adults with obesity and type 2 diabetes, retatrutide produced substantial average weight loss, with around half of people on the highest dose losing at least a fifth of their body weight. Blood sugar, blood pressure and cholesterol also improved. The side-effect profile was largely digestive, with dysesthesia and low blood pressure as notable extras.

It remains a trial result, not a treatment you can get. The important remaining questions are about long-term safety, how it compares directly with existing medicines, and when regulators will review it.

Frequently Asked Questions

What did the retatrutide TRIUMPH-2 results show?

In 1,152 adults with obesity or overweight and type 2 diabetes, retatrutide 12 mg produced average weight loss of 20.8% at 80 weeks if everyone had stayed on treatment, or 18.8% counting everyone including those who stopped. That compares with 4.0% and 5.1% on placebo. HbA1c fell by up to 1.6 percentage points on average.

Is the 20.8% figure new?

No. Lilly announced the 20.8% figure in July 2026. The new information is the peer-reviewed Lancet paper, including responder rates, the more conservative 18.8% analysis, HbA1c targets, blood pressure and cholesterol changes, and additional safety data.

Would everyone lose 20% on retatrutide?

No. On the 12 mg dose, about half of participants (52.0%) lost at least 20% of their body weight, and about a third lost less than 15%. Individual results vary widely.

Is retatrutide approved in the UK?

No. Retatrutide is investigational and has not been authorised by the MHRA. Lilly plans to apply to the US FDA in early 2027 and has not announced a UK application date.

What were the main side effects in TRIUMPH-2?

Mainly diarrhoea, nausea, constipation, vomiting and reduced appetite, which were more common at higher doses. Dysesthesia (altered skin sensation) and low blood pressure were also more common than on placebo. Between 4% and 12% of people on retatrutide stopped because of side effects, depending on dose, compared with 5% on placebo.

Sources

• Bellido V, le Roux CW, Ekinci EI, et al. Retatrutide in adults with obesity and type 2 diabetes (TRIUMPH-2): a double-blind, parallel-group, randomised, placebo-controlled, phase 3 trial. The Lancet, published online 29 September 2026. doi:10.1016/S0140-6736(26)01861-1
• Eli Lilly and Company, detailed TRIUMPH-2 results release, 29 September 2026
• Eli Lilly and Company, TRIUMPH-2 and TRIUMPH-3 topline results release, 23 July 2026
• ClinicalTrials.gov, NCT05929079
• MHRA, No summer shortcut for safe weight loss, 24 July 2026
• Victorian Department of Health, Toxicity linked to unapproved peptide product labelled Retatrutide, 19 June 2026
• Garvey WT, et al. Tirzepatide once weekly for the treatment of obesity in people with type 2 diabetes (SURMOUNT-2). The Lancet 2023;402:613–626. PubMed

This article is for information purposes only and does not constitute medical advice. Always consult a qualified healthcare professional before starting any treatment.