Retatrutide: What Phase 2 Found and Phase 3 Is Checking
Here is what researchers saw in people taking retatrutide. This isn't a clinic or seller; testing hasn't finished, so you don't have an approved drug.
What retatrutide is and what it may change
What is retatrutide, and can your doctor prescribe it now? Retatrutide remains a test drug.
Eli Lilly is studying it for obesity, type 2 diabetes, and related health problems. In your body, the drug works with three hormones that affect hunger, insulin, and calorie use.
One is GLP-1, which helps curb hunger. GIP prompts insulin after food, while glucagon can raise calorie use.
In a 48-week Phase 2 study, the top group had an average loss of 24.2% of starting weight. That was more than earlier approved drugs had shown in similar studies. Those studies did not put the drugs head to head.
By mid-2026, every country still treated retatrutide as unapproved, so your doctor couldn't prescribe it. Each claim here points you to its published source.
People also describe using the drug outside studies, but those accounts aren't proof. You can read their claims and weigh the known risks on the effects page.
What Phase 2 found about your liver, blood sugar, and weight
Two Phase 2 studies from 2023 give the clearest human results so far. Phase 2 is a mid-stage test for benefit and common harm.
In 2023, the obesity study gave 338 adults one shot each week into the fat just under the skin. The doses were 1, 4, 8, or 12 mg for 48 weeks.
Average weight changed −24.2% at 12 mg, versus −2.1% with placebo, the comparison shot without retatrutide [1]. The 8 mg group changed −17.3%.
Nausea, diarrhea, and vomiting were mostly mild or moderate. Faster heart rates appeared more often as amounts rose and peaked near week 24 [1].
In the 2023 Phase 2 diabetes study, 281 adults received 0.5–12 mg weekly for 36 weeks. The team raised it little by little and watched each person.
One blood test shows how sugar ran across the prior three months. At 24 weeks, it fell −2.02% with 12 mg and only −0.01% with placebo.
Lower results mean better sugar control. The report gives the change, not your ending number.
Weight fell −16.94%, compared with −3.00% at 36 weeks [2]. Researchers saw no deaths or dangerous sugar drops; 35% had mild or moderate stomach trouble [2].
A smaller study enrolled 98 adults with fatty liver disease and obesity. At 12 mg, liver fat fell −82.4% by 24 weeks; 86% got under the normal cutoff of 5% on a scan [5].
The liver change lasted through 48 weeks and measured −86.0% [5]. Longer studies must weigh those gains against possible harm to your health.
What the three hormones may change in your body
Retatrutide is a lab-made 39-amino-acid chain, meaning small protein pieces linked together. Its shape lets it copy parts of three hormones [3].
In your body, the first is GLP-1, a hunger hormone. It may dull your hunger. As sugar rises, it also helps your body put out insulin. After meals, another hormone helps your body put out insulin, while glucagon can raise calorie use.
In 2024, researchers studied frozen lab samples to see where retatrutide touched three proteins on cells [3]. These were pictures of samples, not medicine inside your body.
In lab-grown cells, all three proteins reacted, but with different strength [3]. The protein that listens for glucagon reacted least.
The glucagon action makes retatrutide different from drugs that mimic only the other two hormones. Phase 2 suggests this action may raise calorie use and help clear liver fat [6].
In 2025, one review described the loss of about 24% at 12 mg over 48 weeks as unusually large beside older treatments [6]. The review drew that comparison across separate studies, so it can't tell how much weight you would lose or what harm you might face.
What Phase 3 still has to find out for you
Phase 3 is the large study stage before a maker can seek approval. Eli Lilly calls its group of these studies TRIUMPH.
In mid-2026, several studies remained unfinished, so their answers weren't ready for you.
- TRIUMPH-3: This study follows adults who have obesity as well as heart disease [9].
- A heart and kidney study: Researchers are tracking both organs over time [10].
Other TRIUMPH studies include people with type 2 diabetes or long-term kidney disease. One also compares retatrutide with tirzepatide; see retatrutide vs tirzepatide for that question.
In 2025, one review found 14 drugs in active Phase 3 obesity studies [7]. Retatrutide was among the drugs furthest along, but that doesn't tell you whether it will pass.
Your doctor still lacks long-term facts on the heart, kidneys, and whether weight stays off. You need proof of better health, not merely better Phase 2 test numbers.
What does retatrutide do to hunger, sugar, and fat
Retatrutide copies the action of three hormones in your body. Together they may ease your hunger, help release insulin after food, and raise calorie use.
Phase 2 brought weight loss and lower three-month blood-sugar results. Their livers and blood also held less fat [1][2][5][6].
Average body weight changed −24.2% at 12 mg after 48 weeks [1]. In the diabetes study, the three-month sugar test fell −2.02% at 12 mg after 24 weeks [2].
Liver fat fell −82.4% at 12 mg after 24 weeks [5]. A 2024 review said blood-fat and other heart-risk test numbers improved [8].
The review did not show that people had fewer heart attacks. Your own result also can't be read from an average across a group.