This article is educational and summarizes published research and news reports. It is not medical advice. Retatrutide, EloraTZP, CagriSema, and trevogrumab are investigational and not FDA-approved. Talk to your prescriber before making any medication decisions.
The 30-second answer
TRIUMPH-2 is the Phase 3 trial that tested retatrutide in the group that has historically had the hardest time losing weight on any medication: adults who have both obesity and type 2 diabetes. The topline numbers came out in July. The full data, released on September 29, 2026, fill in the details, and they hold up.
On the highest 12 mg dose, the average participant lost about a fifth of their body weight in 80 weeks, cut their A1C by roughly one and a half points, and saw meaningful drops in triglycerides, blood pressure, waist size and inflammation. For people with type 2 diabetes, those are among the largest weight reductions ever reported in a drug trial. NBC News described it as the most weight loss recorded in a diabetes drug trial so far (NBC News).
Below, we walk through the numbers, explain the two different ways the results are reported (this matters more than it sounds), and cover what the side-effect data actually show.
Why type 2 diabetes is the hardest test
People with type 2 diabetes consistently lose less weight on GLP-1 medications than people without it. Endocrinologist Juan Pablo Frías, a TRIUMPH-2 co-author, put it plainly at the meeting: in multiple studies, including bariatric surgery studies, it is harder for people with type 2 diabetes to lose weight, "even with the highest doses of GLP-1 or the dual GIP/GLP-1 agonist tirzepatide" (Medscape).
Why that happens is not fully understood. Retatrutide's third target, the glucagon receptor, raises energy expenditure, which is one reason researchers hoped it might close some of that gap.
For context, NBC News noted that semaglutide has produced up to about 10% weight loss in people with type 2 diabetes, and tirzepatide up to about 15%. Those were separate trials, not head-to-head comparisons, so treat them as a rough frame of reference rather than a ranking. Erasmus Medical Center professor Elisabeth van Rossum, who was not involved in the trial, called the new data "a major step forward from purely glucose-oriented treatment to obesity-oriented treatment for type 2 diabetes" (Medscape).
How the trial was designed
| Detail | TRIUMPH-2 |
|---|---|
| Phase | Phase 3, randomized, double-blind, placebo-controlled |
| Participants randomized | 1,152 adults (from 2,047 screened) |
| Who was eligible | BMI of 27 or higher, type 2 diabetes with A1C between 6.5% and 10.5% |
| Arms | Retatrutide 4 mg, 9 mg, 12 mg or placebo, once weekly (1:1:1:1) |
| Duration | 80 weeks, plus 4 weeks of follow-up |
| Where | 92 sites in 8 countries, including the U.S. |
| Average starting point | 234.6 lb, BMI 38.2, A1C 7.7%, age 55 |
| Background care | Diet counseling and physical activity guidance; 92% were on at least one oral diabetes medication |
Sources: EurekAlert and Lilly's press release.
Every participant started at 2 mg weekly, and the dose stepped up every four weeks until reaching the assigned target. The 12 mg group went 2, 4, 6, 9 and then 12 mg. The protocol allowed dose reductions for people who struggled with side effects, which becomes important when you read the results.
The weight loss numbers
You will see two different sets of numbers in the coverage of this trial. Both are correct. They answer different questions.
- The efficacy estimand asks: what happens if people take the drug as intended? This is the number Lilly leads with.
- The treatment-regimen estimand asks: what happens across everyone who was assigned the drug, including people who stopped taking it? This is closer to what happens in the real world, and it is the number The Lancet paper and the EASD press materials lead with.
Average weight change at 80 weeks
| Arm | Efficacy estimand | Treatment-regimen estimand |
|---|---|---|
| Retatrutide 4 mg | −12.7% (−29.8 lb) | −11.9% |
| Retatrutide 9 mg | −19.1% (−45.4 lb) | −16.8% |
| Retatrutide 12 mg | −20.8% (−49.6 lb) | −18.8% |
| Placebo | −4.0% (−9.3 lb) | −5.1% |
Sources: Lilly (efficacy estimand) and EurekAlert / The Lancet (treatment-regimen estimand).
Two more data points stand out. Among participants who started with a BMI of 35 or higher, the 12 mg dose produced an average loss of 60.8 lb (23.4%). And by the end of the trial, 59.5% of people on 12 mg had dropped below the BMI threshold for obesity.
How many people hit major milestones
| Lost at least… | 4 mg | 9 mg | 12 mg | Placebo |
|---|---|---|---|---|
| 15% of body weight | 36.6% | 62.2% | 67.0% | 6.4% |
| 20% of body weight | 24.0% | 45.3% | 52.0% | 1.5% |
| 25% of body weight | 10.8% | 30.6% | 34.9% | 0.8% |
Efficacy estimand, from Lilly's release. Under the treatment-regimen estimand, 47% of the 12 mg group lost at least 20% and 31% lost at least 25% (EurekAlert).
One pattern worth noticing: the jump from 9 mg to 12 mg was small, about 1.7 percentage points of body weight. The jump from 4 mg to 9 mg was much larger. That plateau between the two higher doses is one reason clinicians will be interested in how dosing is handled if the drug is approved.
The blood sugar numbers
A1C is a measure of average blood sugar over the previous two to three months. The trial started at an average of 7.7%.
| Arm | A1C change | Reached A1C ≤6.5% | Reached A1C <5.7% (normal) |
|---|---|---|---|
| Retatrutide 4 mg | −1.4 points | 73.1% | 28.4% |
| Retatrutide 9 mg | −1.6 points | 79.2% | 40.0% |
| Retatrutide 12 mg | −1.5 points | 79.0% | 39.3% |
| Placebo | −0.2 points | 26.3% | 4.4% |
Efficacy estimand, from Lilly. Lilly notes the below-5.7% endpoint was not controlled for multiple comparisons, so it should be read as supportive rather than definitive.
Notice that A1C reduction was essentially the same at 9 mg and 12 mg. The weight benefit kept climbing slightly with dose, but the blood sugar benefit leveled off. There were no episodes of severe hypoglycemia in the trial (Medscape).
Dr. Michelle Ponder of Duke University, who was not involved in the trial, told NBC News that reaching a 5.7% A1C means "that their diabetes went into remission." That is a strong way to put it. Remission is typically defined over longer periods and off medication, so it is fairer to say these participants reached normal-range blood sugar while on treatment.
Heart and metabolic markers
Weight and blood sugar get the headlines, but the cardiovascular risk markers may matter just as much for this population. At the 12 mg dose, Lilly reported average reductions of:
- Triglycerides: down 39.5%
- Non-HDL cholesterol: down 19.6%
- Systolic blood pressure: down 10.8 mmHg
- Waist circumference: down 6.7 inches (16.9 cm)
- High-sensitivity C-reactive protein (an inflammation marker): down 58.3%
These are risk-factor improvements, not proof of fewer heart attacks or strokes. Lilly is running a separate cardiovascular and kidney outcomes trial to answer that question directly. You can follow it on our retatrutide cardiovascular outcomes page.
Side effects: what the data show
The side-effect profile was similar to other GLP-1-based medications, with gastrointestinal problems most common and most frequent at the higher doses.
| Side effect | 4 mg | 9 mg | 12 mg | Placebo |
|---|---|---|---|---|
| Diarrhea | 27.4% | 33.5% | 33.6% | 13.2% |
| Nausea | 13.7% | 20.8% | 28.0% | 8.0% |
| Constipation | 14.0% | 16.2% | 16.8% | 9.4% |
| Decreased appetite | 5.8% | 12.3% | 17.1% | 4.5% |
| Vomiting | 5.5% | 10.2% | 15.7% | 4.2% |
| Dysesthesia (skin burning or discomfort) | 4.5% | 5.6% | 7.3% | 0.7% |
| Urinary tract infection | 3.8% | 6.3% | 8.0% | 6.6% |
| Stopped due to side effects | 3.8% | 11.6% | 7.7% | 4.9% |
Source: Lilly press release.
A few points to keep in perspective:
- Only about 2% of people on the two higher doses stopped because of gastrointestinal side effects (Medscape). Most of the discomfort was mild to moderate and resolved during treatment.
- Dysesthesia has now shown up across the retatrutide program. None of the TRIUMPH-2 cases were severe or serious. Erasmus Medical Center professor Elisabeth van Rossum, who was not involved in the trial, said it is "not often a reason to stop treatment but something to be aware of and monitor as clinicians."
- Low blood pressure (including dizziness on standing) occurred in 1% to 6% of retatrutide participants versus under 1% on placebo. This is worth knowing for anyone already taking blood pressure medication.
- Seven participants died during the trial (six across the retatrutide groups and one on placebo). Investigators judged all deaths to be unrelated to the study drug (EurekAlert).
For a deeper look at managing these symptoms, see our guide to managing GLP-1 side effects and our retatrutide side effects hub.
The caveats experts raised
The results are strong, but independent experts flagged several open questions at EASD (Medscape):
- Dose reductions blur the dose groups. Participants could step down for tolerability but still be counted in their original group. Someone in the "12 mg" arm may have spent months on 9 mg. Van Rossum said the groups are "very much mixed up" and that real-world data will be needed.
- No body-composition data yet. The trial did not report how much of the lost weight was fat versus muscle. TRIUMPH-3 will include DEXA scans. Because glucagon affects metabolism, its effect on muscle could go either way, and nobody knows yet.
- Titration may need to be slower. Van Rossum noted that with all GLP-1-based therapies, it matters to "start low and go slow," possibly slower than the schedule used here. Our retatrutide titration explainer covers how the trial schedules work.
- Long-term data are still needed. Eighty weeks is a long trial, but type 2 diabetes is a lifelong condition.
How TRIUMPH-2 fits the bigger retatrutide picture
TRIUMPH-2 is one piece of a larger program. On the same day, results from another retatrutide trial in people without diabetes were published in the New England Journal of Medicine, with average losses of up to 25% over 80 weeks and up to 30% over 104 weeks in people with severe obesity (NBC News). We covered the earlier readouts in our retatrutide weight loss results guide and our breakdown of the TRIUMPH-2 and TRIUMPH-3 topline results.
TRIUMPH-2 also included a separate sub-study in people with moderate to severe obstructive sleep apnea. Those results have not been released yet. Lilly says they will be presented at a future medical meeting.
What this means if you have type 2 diabetes
If you have type 2 diabetes and obesity, the honest takeaway is this: a medication that may help you lose a fifth of your body weight and bring your blood sugar into the normal range is likely coming, but it is not here yet.
- Retatrutide is not approved anywhere in the world. Lilly plans to file with the FDA in the first quarter of 2027, so a U.S. decision is unlikely before 2028. See our retatrutide FDA approval timeline.
- Products sold online as "retatrutide" are not the trial drug. The FDA has said retatrutide cannot be legally compounded, and Lilly is suing sellers of unapproved versions. Our counterfeit safety guide explains the risks.
- Approved options already work. Tirzepatide (Mounjaro, Zepbound) and semaglutide (Ozempic, Wegovy) are available today. As Dr. Ponder told NBC News, retatrutide "may be too strong for some patients," and people with milder diabetes or modest excess weight may be better served by current medications.
- Ask about clinical trials or expanded access. Lilly offers a limited expanded access program for some patients who meet strict medical criteria.
Frequently asked questions
How much weight did people lose on retatrutide in TRIUMPH-2?
On the 12 mg dose, adults with type 2 diabetes and obesity lost an average of 20.8% of body weight (49.6 lb) over 80 weeks under the efficacy estimand, or 18.8% counting everyone regardless of whether they stayed on treatment. Placebo groups lost 4.0% to 5.1%.
Did retatrutide lower A1C?
Yes. A1C fell by 1.4 to 1.6 percentage points from a 7.7% baseline, compared with 0.2 points on placebo. Up to 79% reached an A1C of 6.5% or lower, and up to 40% reached the normal range below 5.7%.
What are the main side effects of retatrutide?
Mostly gastrointestinal: diarrhea, nausea, constipation, vomiting, and decreased appetite, more common at higher doses. Dysesthesia (a skin burning sensation) occurred in up to 7.3% of participants, and low blood pressure in 1% to 6%.
When will retatrutide be approved?
Retatrutide is not approved anywhere. Lilly plans to submit it to the FDA in the first quarter of 2027, so a U.S. approval decision is unlikely before 2028.
Is TRIUMPH-2 the same as the earlier retatrutide results?
No. The July 2026 announcement was a topline summary. The September 29, 2026 release is the full dataset, published in The Lancet and presented at the EASD meeting in Milan.
The bottom line
TRIUMPH-2 shows that retatrutide can produce weight loss in people with type 2 diabetes that was previously seen only with bariatric surgery, along with large improvements in blood sugar and heart risk markers. The open questions are dosing, muscle preservation, and long-term safety. Until approval, the best move is to work with your prescriber on the effective medications available today.
Sources
- Eli Lilly press release: TRIUMPH-2 results (September 29, 2026)
- EurekAlert / The Lancet: TRIUMPH-2 publication summary
- Medscape: Retatrutide yields significant weight loss in T2D
- NBC News: Retatrutide in type 2 diabetes
- The Guardian: Retatrutide coverage, September 29, 2026
Educational content written by Rolando Valenzuela, founder of GLPTree. Not medical advice. Talk to your prescriber before starting, stopping, or switching any medication.