What have retatrutide studies found?
Human tests found large weight loss, nausea, and a quicker resting pulse. Longer safety answers aren’t ready.
What do we know about retatrutide now?
Retatrutide is being tested for weight loss and high blood sugar. It copies three hormones, which are body messages carried in your blood.
Phase 1 started as a small check for harm. Phase 2 then followed 338 adults with obesity and looked harder at weight and health.
At the largest amount tested, average weight fell 24.2% in 48 weeks [1]. That average topped results for approved drugs at the time, but your own change could be quite different.
As of 2026, no country had approved retatrutide. Phase 3 was still testing benefits and harms in larger groups.
You can’t get retatrutide by prescription. The effects page separates human test results from untested reports by people who bought vials sold for lab research.
What does retatrutide change in your body?
Retatrutide copies three hormones, or body messages carried in your blood. The messages do different jobs: 1 curbs hunger, 1 helps control blood sugar, and 1 may burn more stored fat.
Food raises the sugar in your blood. The pancreas, an organ behind your stomach, then sends out insulin so sugar can move from your blood into your cells, where it can be used instead of staying too high.
Most drugs in this family act like one body message, while tirzepatide acts like two. Doctors can prescribe tirzepatide for type 2 diabetes; retatrutide adds the third message.
In Phase 1, doctors first learned how people handled the drug. In 2024, lab work showed that retatrutide could start all three actions; Phase 2 then checked what happened in people [3].
Why did studies give retatrutide each week?
Retatrutide is made from amino acids, the small parts that form protein. Scientists changed one part so your body removes the drug slowly.
The changed part lets retatrutide travel with albumin, a common blood protein. Because your body clears it slowly, one shot stayed active for days.
About half the drug remains after close to a week. That long stay is why the studies gave it weekly [4].
Two actions reduce hunger and let insulin move blood sugar into cells after meals. Those actions may also help fat cells use sugar for energy.
The third action may tell the liver to draw on stored fat. Less food, plus greater use of stored fat, may both lower weight.
That same action may also speed your resting pulse [8]. In Phase 2, the pulse climbed highest around 24 weeks and then eased somewhat [1].
What did the Phase 2 studies find?
During 2023, the middle-sized Phase 2 weight study followed 338 adults with obesity. People given 12 milligrams, a measure of drug weight, each week lost 24.2% on average in 48 weeks, versus 2.1% with placebo, an inactive shot [1].
Among those given 12 milligrams, more than eight in ten lost over 15% of their weight. That size of loss may change health as well as clothing size.
In 2023, another Phase 2 study followed 281 adults with type 2 diabetes for 36 weeks. With 12 milligrams, their long-term blood-sugar reading fell 2.02%, a large drop, and weight fell 16.94%.
With placebo, the readings changed by 0.01% and 3.0% [2]. No one had blood sugar fall so far that help was needed.
A further Phase 2 test studied fatty liver disease. With 12 milligrams, liver fat fell 82.4% in 24 weeks, and 86% reached a normal level [5].
Doctors chose and watched the people in all three tests. Retatrutide research gives the full results and the questions still open in Phase 3.
What did the first Phase 3 report find?
The first large Phase 3 report followed 537 adults with type 2 diabetes. The study was one of several Phase 3 tests run by Eli Lilly.
With 12 milligrams, the long-term blood-sugar reading fell 1.94%, and weight fell 15.3% in 40 weeks. Placebo brought drops of 0.81% and 2.6%; doctors rated most stomach problems mild or moderate, and nobody needed help for very low blood sugar while doctors watched them closely [12].
Heart and kidney tests haven’t reported, so those long-term answers are missing. Retatrutide isn’t approved or sold as medicine while the review remains unfinished.
The retatrutide results page covers each human test. You can also read retatrutide vs tirzepatide; tirzepatide is the approved drug in that comparison.