Adults with type 2 diabetes and a body mass index of 35 or higher who took the highest dose of retatrutide lost an average of 23.4% of their body weight, about 60.8 pounds, over 80 weeks. The figure comes from the full TRIUMPH-2 results, now peer-reviewed and published in The Lancet on Sept. 29, 2026, alongside a presentation at the European Association for the Study of Diabetes meeting in Milan.
Update Note: This article reports new information involving Eli Lilly's experimental drug retatrutide following MedicalDaily's earlier coverage. (Latest verified update: Sept. 29, 2026; sources: The Lancet and Eli Lilly.)
Two limits belong at the top. The trial was funded by Eli Lilly, the drug's maker, and the 23.4% figure comes from a subgroup analysis that assumes people stayed on treatment. Retatrutide is not approved by the FDA or any other regulator, so no doctor can prescribe it outside a clinical trial.
For Americans managing both diabetes and obesity, the data address a common family question. Weight-loss drugs have historically worked less well in people with diabetes, and many households with a relative on insulin or metformin wonder whether one drug could ease both conditions.
Inside the TRIUMPH-2 Numbers
The phase 3 trial randomly assigned 1,152 adults with type 2 diabetes and obesity or overweight to weekly injections of retatrutide at 4 mg, 9 mg or 12 mg, or to a placebo. Participants started with an average weight of 234.6 pounds, an average BMI of 38.2, and an average A1C of about 7.7%, according to Lilly's announcement.
Under the analysis Lilly highlights, called the efficacy estimand, average weight loss at 80 weeks was 12.7% at 4 mg, 19.1% at 9 mg and 20.8% at 12 mg, compared with 4.0% on placebo. A second, more conservative analysis that counts everyone regardless of whether they stopped treatment showed smaller losses of 11.9%, 16.8% and 18.8%, against 5.1% on placebo, Pharmacy Times reported.
Blood sugar improved as well. A1C fell by 1.4, 1.6 and 1.5 percentage points across the three doses, versus 0.2 on placebo. Up to 40% of participants reached an A1C below 5.7%, the normal, non-diabetic range, and 59.5% of those on 12 mg no longer met the BMI cutoff for obesity.
At the top dose, the company also reported a 39.5% drop in triglycerides, a 19.6% drop in non-HDL cholesterol, a 10.8 mmHg fall in systolic blood pressure, and a 58.3% reduction in hsCRP, a marker of inflammation. These are risk factors, not heart attacks or strokes, and the trial was not designed to show fewer cardiovascular events.
Three Hormone Targets and the Side Effects That Came with Them
Lilly describes retatrutide as a single molecule that activates receptors for three hormones: GIP, GLP-1 and glucagon. Semaglutide, sold as Ozempic and Wegovy, targets GLP-1 alone, while tirzepatide, sold as Mounjaro and Zepbound, targets GLP-1 and GIP. Retatrutide adds glucagon, a hormone that acts mainly on the liver and the body's energy use.
That extra pathway may help explain the size of the weight loss, but it comes with trade-offs. Diarrhea affected 27.4% to 33.6% of people on retatrutide versus 13.2% on placebo, nausea affected up to 28.0% versus 8.0%, and vomiting up to 15.7% versus 4.2%. Dysesthesia, an abnormal or uncomfortable skin sensation, occurred in 4.5% to 7.3% of retatrutide users compared with 0.7% on placebo.
Treatment discontinuation due to side effects reached 11.6% at 9 mg and 7.7% at 12 mg, compared with 4.9% on placebo. For families, stomach symptoms like these can disrupt work, meals and sleep.
"Results such as these may change what we set out to achieve with a single therapy for adults living with type 2 diabetes and obesity," said Dr. Juan P. Frías, medical director and principal investigator at the Los Angeles Institute for Metabolic Research, in Lilly's release.
Independent pharmacists struck a more measured tone. Philip Newland-Jones of the University of Southampton told The Pharmaceutical Journal that weight-loss drugs have tended to work less well in people with diabetes, "making the average of almost 21% weight loss with retatrutide especially impressive." Helen O'Neil, a senior medicines optimization pharmacist at NHS North East and North Cumbria Integrated Care Board, said side effects "appear similar to other incretin-based therapies, but head-to-head studies are needed to determine its place in treatment pathways."
Earlier Reporting, Approval Timing and Real Risks for Patients
MedicalDaily previously reported the company's topline figures ahead of the Milan meeting on Sept. 28, when the results had not yet been published in a journal. The new Lancet paper adds the peer-reviewed analysis, the BMI 35-or-higher subgroup, the conservative treatment-regimen numbers and a fuller side-effect profile.
What has not changed is availability. Lilly plans to submit an application to the FDA in the first quarter of 2027, and a decision would typically take months after that. Price, insurance coverage, and how retatrutide would compare directly against tirzepatide or semaglutide are all unknown.
That gap is where households face the most real risk. MedicalDaily has reported that products sold as retatrutide are already appearing at medical spas and online sellers. Those products are not the drug tested in TRIUMPH-2, and their contents, dose and sterility cannot be verified.
People with type 2 diabetes who are curious about these results can bring them to their next appointment and ask whether an approved option, such as tirzepatide or semaglutide, fits their health history and insurance plan. Do not stop or change prescribed diabetes medication without speaking with a health care professional, because sudden changes can affect blood sugar control.
Anyone already using an injectable sold as retatrutide should tell a clinician. Severe abdominal pain, persistent vomiting, signs of dehydration or very low blood sugar warrant prompt medical care.
Peer review has now confirmed large weight and blood sugar improvements in a Lilly-funded trial, with the biggest gains in people with a higher starting BMI. For now, the useful step is a conversation with a clinician about approved treatments while an FDA review, expected after early 2027, plays out.
Key Questions Answered
What did the new Lancet paper show about retatrutide?
In the TRIUMPH-2 trial of 1,152 adults with type 2 diabetes and obesity or overweight, the 12 mg dose produced 20.8% average weight loss at 80 weeks under the analysis Lilly highlights. People with a starting BMI of 35 or higher lost 23.4% on average.
Is retatrutide approved or available by prescription?
No. Retatrutide is investigational and is available only to clinical trial participants. Lilly plans to apply for FDA approval in the first quarter of 2027.
How is retatrutide different from Ozempic or Mounjaro?
Ozempic targets one hormone receptor, GLP-1, and Mounjaro targets two, GLP-1 and GIP. Retatrutide activates those two plus the glucagon receptor.
What side effects were reported?
Diarrhea, nausea, and vomiting were the most common. About 4.5% to 7.3% of people on retatrutide reported dysesthesia, an unusual skin sensation, versus 0.7% on placebo.
Who paid for the study?
Eli Lilly, the drug's maker, funded the trial. Head-to-head studies against existing drugs have not yet been reported.
Should people with diabetes buy retatrutide online?
No. Products sold online or at spas as retatrutide are not approved, and their contents cannot be verified. Talk with a clinician about approved options instead.
Published by Medicaldaily.com
