Status as of October 5, 2026. This area changes fast, so check the date.
Retatrutide is a once-weekly injection from Eli Lilly. It activates three receptors: GLP-1, GIP and glucagon. Semaglutide hits one of those. Tirzepatide hits two. You can read the basics on our retatrutide page, or go further in our retatrutide deep dive.
If you follow GLP-1 news, you have seen the headlines. Here are the numbers behind them, and the limits.
TRIUMPH-1 enrolled 2,339 adults with obesity or overweight and at least one weight-related condition. None had diabetes. Lilly announced the results on May 21, 2026.
At 80 weeks, people on the 12 mg dose lost an average of 28.3% of their body weight. The 9 mg group lost 25.9%. The 4 mg group lost 19.0%. Placebo lost 2.2%. Those figures use the efficacy estimand, which estimates the effect if everyone had stayed on treatment.
The treatment-regimen estimand is more conservative. It counts everyone as randomized, whether or not they kept taking the drug. On that measure, the 12 mg dose came in at 25.0%, against 3.9% for placebo. Both numbers are worth knowing.
A smaller group of 532 people with a BMI of 35 or higher continued into a blinded extension. They had finished the 80 weeks and tolerated their dose. At 104 weeks, the group that started on 12 mg had lost 30.3%. Keep in mind this group was made up of people who were already doing well on the drug.
On July 23, 2026, Lilly reported two more trials.
TRIUMPH-2 studied 1,152 adults with type 2 diabetes. Weight loss at 80 weeks was 12.7% on the 4 mg dose, 19.1% on 9 mg and 20.8% on 12 mg, against 4.0% for placebo. A1c fell by 1.4 to 1.6 points, against 0.2 for placebo.
TRIUMPH-3 studied 1,949 people with a BMI of 35 or higher and established cardiovascular disease. Weight loss was 21.6% at 9 mg and 22.6% at 12 mg, against 3.2% for placebo.
Weight loss is not the same as proven heart benefit. In Lilly’s analysis of TRIUMPH-3, the confidence intervals on major cardiovascular events crossed 1. That means the effect is unresolved. A dedicated outcomes trial, TRIUMPH-Outcomes, is underway to answer it.
Most side effects were gastrointestinal. In TRIUMPH-1, at the 12 mg dose, 42.4% of people had nausea, 32.0% had diarrhea, 26.1% had constipation and 25.3% had vomiting. Placebo rates were much lower.
Dysesthesia also showed up. That is an odd skin sensation, such as tingling or sensitivity. It affected 5.1% to 12.5% of people on retatrutide, depending on dose, and 0.9% on placebo.
Stopping because of side effects rose with dose. In TRIUMPH-1, it was 4.1% at 4 mg and 11.3% at 12 mg. Placebo was 4.9%. In TRIUMPH-3, 13.5% stopped at 12 mg, against 4.8% on placebo.
A bigger number on the scale came with a bigger side effect burden. That tradeoff is part of the story.
Phase 3 results are not an approval. Lilly says it plans to submit to the FDA in the first quarter of 2027. As of today, no application has been filed. After that, FDA reviews the full data package, including long-term safety and manufacturing. That takes months.
Lilly has also set up a limited expanded access program for people who meet certain medical criteria and cannot join a trial. That runs through a healthcare provider.
Because the drug is not approved, anything sold online as retatrutide is not an FDA-reviewed product. In August 2026, FDA sent warning letters to five sellers of peptide products. The letters named retatrutide among other drugs. FDA’s view was that “research use only” labels did not change the fact that the products were being marketed as drugs. We cover what those letters mean in our FDA warning letters post.
We cannot tell you what is in those vials. Neither can the sellers, in any way you can check.
The retatrutide data is strong. It is also early, and the side effects are significant. It is not approved, and a filing is not an approval.
If you are curious about it, the honest path is to watch the FDA process and talk with a doctor about the options that exist today, such as semaglutide and tirzepatide.
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