The new retatrutide type 2 diabetes results show average weight loss of about one-fifth of starting weight in TRIUMPH-2's highest-dose group. That 20.8% figure assumes people stayed on treatment; the broader analysis reported 18.8%. Retatrutide remains investigational, meaning it is still being tested, with no approved product available today.
For someone taking tirzepatide or semaglutide, this is progress toward a possible future option. It does not establish that switching would work better.
What the retatrutide type 2 diabetes results show
As of September 30, 2026, the day this article was written, TRIUMPH-2 has a published paper alongside Lilly's detailed results. Lilly announced the findings on September 29 at a diabetes meeting in Milan. The TRIUMPH-2 paper in The Lancet, 2026 adds detail beyond the earlier headline announcement.
This phase 3 study, a late-stage human trial, enrolled 1,152 adults with type 2 diabetes and overweight or obesity. Their average age was 55.1. They received weekly retatrutide or placebo, a shot without the active drug, for 80 weeks.
Participants had a BMI, a measure of weight relative to height, of at least 27. They were on stable diabetes treatment: diet and exercise alone, or up to three oral medicines. The trial registry describes that selected population. These results do not automatically apply to everyone with diabetes.
Retatrutide is a triple agonist: one molecule activates three hormone receptors, the switches cells use to receive signals. These are GIP and GLP-1, which help regulate blood sugar, and glucagon, which helps release stored fuel. The retatrutide explainer covers how it works.
Why there are two weight-loss numbers
An estimand is the question a trial calculation is designed to answer. Lilly's efficacy estimand assumes everyone stayed on treatment without adding prohibited weight-management treatments. The paper's primary treatment-regimen estimand includes treatment stops, with missing results estimated.
| Assigned group | Weight change: efficacy analysis | Weight change: primary treatment-regimen analysis |
|---|---|---|
| Retatrutide 4 mg | -12.7% | -11.9% |
| Retatrutide 9 mg | -19.1% | -16.8% |
| Retatrutide 12 mg | -20.8% | -18.8% |
| Placebo | -4.0% | -5.1% |
The efficacy figures come from Lilly's September 29 results; the treatment-regimen figures come from the Lancet paper. Both describe group averages, not an individual's expected result.
For someone considering tirzepatide, keeping those assumptions attached to the numbers matters. TRIUMPH-2 compared retatrutide with placebo, not with tirzepatide.
What the retatrutide A1C results mean
A1C is a blood test that reflects average blood sugar over roughly three months. The trial's average starting A1C was 7.7%.
Under Lilly's efficacy analysis, A1C fell by 1.4 percentage points with 4 mg, 1.6 with 9 mg, and 1.5 with 12 mg. Placebo showed a 0.2-point fall. These are percentage-point changes, not relative percentage reductions.
That calculation also assumes participants did not add rescue treatment, meaning extra medicine to control blood sugar.
About four in ten reached an A1C below 5.7%: 40.0% in the 9 mg group and 39.3% in the 12 mg group. Placebo reached 4.4%. Those percentages were reported without an adjustment for testing several outcomes, so chance findings are harder to rule out.
A normal-range number during treatment does not establish diabetes remission: blood sugar staying below the diabetes range without glucose-lowering medicines. A 2021 consensus report in Diabetologia generally defines remission as A1C below 6.5% at least three months after stopping those medicines.
TRIUMPH-2 measured blood sugar while people received treatment. It did not establish that their diabetes would remain below that threshold after treatment ended.
For someone considering semaglutide, these findings cannot replace a discussion of semaglutide's own benefits and side effects. There was no semaglutide comparison group.
Retatrutide side effects in the trial
Stomach and bowel symptoms were common. The table uses the detailed percentages Lilly reported for TRIUMPH-2.
Dysesthesia means an abnormal skin sensation, such as tingling or burning. Adverse events are health problems reported during a trial; reporting one does not by itself prove the drug caused it.
| Reported event | 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% |
| Vomiting | 5.5% | 10.2% | 15.7% | 4.2% |
| Dysesthesia | 4.5% | 5.6% | 7.3% | 0.7% |
| Stopped because of adverse events | 3.8% | 11.6% | 7.7% | 4.9% |
Lilly described the listed events as generally mild or moderate, with most resolving during treatment. Still, some people stopped. The 9 mg group had the highest rate of stopping because of adverse events; it was not a simple highest-dose pattern.
What the news does not mean for treatment today
The study does not establish that retatrutide works better than either tirzepatide or semaglutide. Different trials enroll different people and use different calculations. The tirzepatide and retatrutide comparison explains the broader differences.
As of September 30, 2026, the day this article was written, retatrutide remains outside routine prescribing. FDA's page, current as of September 1, 2026, says retatrutide cannot be used in compounding under federal law. An Australian regulator's September 14, 2026 alert also says no comparable international regulator has approved it.
An online product sold as retatrutide outside Lilly's trials is not Lilly's trial supply; the counterfeit retatrutide report explains why that distinction matters. The retatrutide lawsuits overview covers the separate legal disputes around outside sellers.
Through Promise, tirzepatide and semaglutide are dispensed as compounded medications, which are different from FDA-approved products: the formulations offered here are not FDA-approved. Compounding means a pharmacy prepares a medication for an individual prescription. TRIUMPH-2 does not establish outcomes for those compounded formulations.
A licensed provider may still prescribe an appropriate compounded tirzepatide or semaglutide formulation; that decision is between you and your doctor. At Promise, a licensed U.S. provider reviews every request, and not everyone qualifies.
When will retatrutide be approved?
Lilly's September 29 release says it plans to submit a Biologics License Application in the first quarter of 2027. That is an application asking FDA to review the medicine. A planned filing is not an approval date or a date when prescriptions will become available.
Lilly also says separate TRIUMPH-2 results for obstructive sleep apnea, breathing repeatedly stopping during sleep, will be presented later. The diabetes and weight findings cannot stand in for that analysis.
The useful discussion today is about current blood sugar, weight goals, existing medicines and tolerability, meaning how manageable side effects are. A prescriber weighs those factors and sets the actual dose. The new trial adds information about a possible future medicine; today's treatment decision still rests on the options available now.
