Retatrutide helped people lose weight; lasting safety is unknown.
Phase 2 means early tests of whether a drug helps people. Weight fell −24.2% over 48 weeks; liver fat fell −82.4% over 24 weeks. Phase 3 checks larger groups before any approval review. Here are the gains and risks you can weigh.
Retatrutide copies hormones that affect hunger and sugar
Still being tested, retatrutide copies hormones, the body's chemical messengers. Here you'll learn about the falls in weight and stored liver fat. Eli Lilly developed the drug to bring three effects together. GLP-1 reduces hunger and helps control blood sugar. GIP helps release insulin after eating; insulin helps lower your blood sugar. Glucagon makes your body use more calories, even while you're resting. No approved weight medicine brings all three effects together.
Lasting safety remains uncertain because the studies haven't followed people for years, even though the 48-week test in 338 adults with obesity did show large weight losses. At the highest amount, weight fell 24.2% on average. With placebo, meaning a drug-free shot, weight fell 2.1%. In a smaller liver study, 86% reached normal liver fat by week 24. These were Phase 2 studies: early tests of whether a drug helps. Phase 3 tests use larger groups to check benefits and harms before an approval request.
As of 2026, retatrutide has no prescription use and hasn't gained approval from any drug regulator, including the FDA.
You can read the effects people describe, including what remains unchecked.
Phase 2, early tests of benefit, found large losses
These studies were too brief to settle benefits or harms over years. The Phase 2 test, an early check of benefit, followed 338 adults carrying excess weight in a 48-week study. Some also had another illness. Each week, volunteers received a shot in the fat just below skin. With 12 milligrams, average weight fell −24.2%; with placebo, a drug-free shot, weight fell −2.1% [1]. Researchers tested 1, 4, 8, and 12 milligrams, with the percentages showing the share of starting weight lost and greater losses at higher amounts, but no safe personal amount for you.
The Phase 2 diabetes study was another early test, involving 281 adults with type 2 diabetes. At 24 weeks, the blood test reflecting sugar levels over recent months improved with 12 milligrams. The placebo result barely changed. Weight fell 16.94% by week 36 [2]. A fall in the sugar reading doesn't give you the starting and ending readings. Those aren't stated here, so a full before-and-after comparison isn't possible.
The smaller liver work was a 48-week study. With 12 milligrams, scans showed liver fat down −82.4% after 24 weeks. That means a fall in the fat people started with, rather than a share of their whole liver. Eighty-six percent reached normal liver fat, below 5% [5]. At 48 weeks, liver fat was down −86.0% with 12 milligrams. Glucagon may help liver cells turn stored fat into fuel [7]. Less fat doesn't prove your liver scars would heal.
Separate drug studies can't establish which medicine would serve you best. A review included 26 studies and 15,491 adults without diabetes. At 12 milligrams, retatrutide showed 22.1% weight loss over 48 weeks. The review also calculated a range around the average to allow for chance. Its 95% means this way of finding a range would cover the true average ninety-five times in a hundred if similar studies were repeated. The range doesn't show the spread of individual people's losses. Tirzepatide at 15 milligrams showed 17.8% loss over 72 weeks. Semaglutide at 2.4 milligrams showed 13.9% over 68 weeks [9]. Different people and study lengths make these rough comparisons.
You can see each study's results or read more about the research.
Retatrutide may change how your body uses food
Retatrutide reaches cell parts receiving messages from the three hormones. The GLP-1 effect slows the passage of a meal out of your stomach. You stay full longer, and hunger falls through effects in the brain. GIP helps release insulin after eating and changes how fat tissue handles fuel. Glucagon helps your body burn calories at rest. Glucagon also helps break down fat stored in your liver.
Burning more fuel may add to the effect of eating less, beyond GLP-1 hunger control. Earlier GLP-1 drugs copy the hunger hormone alone. Other drugs copy both GLP-1/GIP, adding help with insulin release. Retatrutide brings in glucagon as well. Cells in a dish responded to all three effects [3]. The strongest response was to GIP, but those cell tests can't measure your future weight loss or symptoms, which need checking through studies that follow people over longer use.
Other drugs' approval does not cover retatrutide
By mid-2026, retatrutide lacked drug approval anywhere. You couldn't receive the drug as an approved medicine. Eli Lilly's Phase 3 program, the larger tests before an approval request, is called TRIUMPH. Researchers are studying obesity, type 2 diabetes, and lasting heart and kidney illness. The company hadn't filed an approval request. Finished Phase 3 tests and review of their findings would come first.
Tirzepatide is approved for type 2 diabetes and obesity. Semaglutide also has approval for type 2 diabetes and obesity. Retatrutide may follow them, but hasn't reached that point. Approval for an earlier drug can't answer your safety questions about this one.
Study enrollment is the way to receive checked retatrutide
A registered medical study can provide checked retatrutide and staff who watch your health. TRIUMPH is one such study. No approved medicine is available outside studies. Sellers offer bottles labeled for research, but you can't rely on their contents. The wrong drug, wrong amount, or germs could be inside. A seller's label doesn't provide the medical checks you'd get in a study.
During 2025, retatrutide sellers received more than 50 FDA letters warning of breaches of drug law. Those bottles aren't the finished medicine Eli Lilly might eventually seek approval to sell.
No date for retatrutide by prescription has been confirmed
You had no confirmed date from Eli Lilly or drug regulators in mid-2026. Phase 3 means larger tests before any approval request. The weight and sugar studies include TRIUMPH-1, TRIUMPH-2, and TRIUMPH-3. Separate work checks heart and kidney health. Researchers must finish the studies and review the findings before requesting approval.
Analysts used Phase 3 timing to guess at an approval request in 2026–2027. That guess isn't a promised release date. Completed Phase 3 findings would still need review. You can't plan treatment around an analyst's guess.