Clinical update · checked September 30, 2026
Retatrutide is in late-stage (Phase 3) trials. It is not approved and isn’t available as a prescription medicine. Five Phase 3 trials have shared results, and three have been published in medical journals, the latest two in September 2026. Lilly says it plans to ask the FDA for approval in the first quarter of 2027. 1234
Last updated Medical review in progress
25.0%
Average weight lost on 12 mg over 80 weeks in TRIUMPH-1, counting everyone who started (NEJM) 2
How it works
Retatrutide is one molecule that switches on three hormone receptors. Pick a drug to see which receptors it acts on.
Receptor map
Retatrutide acts on all three: GIP, GLP-1 and glucagon. It is still being studied and is not approved. Acts on 3 of 3 54
GLP-1
A gut hormone released after eating. It helps the body release insulin when blood sugar is high, slows the stomach and lowers appetite. 13
GIP
Another gut hormone released after eating. It also helps the body release insulin when blood sugar is high. 14
Glucagon
A hormone from the pancreas. It tells the liver to release sugar and may raise the energy the body burns. This is the new part in retatrutide. 5
The receptor map describes how the drugs are designed to act; it does not predict what any one person will experience. 5
The story so far
Each step below is a published paper or an official company result. The numbers are trial averages, not what any one person can expect.
Aug 2022
Discovery
Lilly scientists described a new molecule, then called LY3437943, built to switch on three hormone receptors at once: GLP-1, GIP and glucagon. Earlier drugs switch on one or two of these. In lab studies and a first study in people, it lowered blood sugar and body weight. 5
3
hormone receptors switched on by one molecule
Oct 2022
Phase 1
A small 12-week study in people with type 2 diabetes tested rising doses. Half of each dose was still in the body after about 6 days, which is why it can be given once a week. A1c, a measure of average blood sugar over about 3 months, fell by up to 1.2 points. Weight fell by up to about 9 kg (20 lb). 6
~6 days
for half the drug to leave the body
1.2
A1c points lower at 12 weeks, best group
Jun 2023
Phase 2
Two larger Phase 2 trials were published on the same day. In 338 adults with obesity, people on the highest dose (12 mg) lost 24.2% of their body weight on average after 48 weeks, against 2.1% on placebo. In 281 adults with type 2 diabetes, A1c fell by about 2 points on 12 mg after 24 weeks. 78
24.2%
weight lost at 48 weeks on 12 mg
2.0
A1c points lower at 24 weeks on 12 mg
Dec 2025
First Phase 3 result
The first Phase 3 result came from 445 adults with obesity and knee osteoarthritis. After 68 weeks, people on 12 mg who stayed on treatment lost 28.7% of their weight on average, about 71 lb. Their knee pain scores fell by about three quarters, against about 40% on placebo. This trial also showed a side effect that is not common with older drugs: dysesthesia, an unusual skin feeling such as tingling. 9
28.7%
weight lost at 68 weeks on 12 mg
74%
drop in knee pain score on 12 mg
Mar 2026
Type 2 diabetes
TRANSCEND-T2D-1 followed 537 adults with type 2 diabetes for 40 weeks. A1c fell by 1.7 to 2.0 points across the doses, against 0.8 on placebo. People on 12 mg also lost 16.8% of their weight. The full results were published in The Lancet in June 2026. 1217
2.0
A1c points lower on 9 mg
16.8%
weight lost on 12 mg
May 2026
The main obesity trial
TRIUMPH-1 is the largest trial so far: 2,339 adults with obesity or overweight and no diabetes. After 80 weeks, people on 12 mg who stayed on treatment lost 28.3% of their weight, against 2.2% on placebo. Almost half of them (45.3%) lost 30% or more. A group with a BMI of 35 or higher who kept going to 104 weeks lost 30.3%. 10
28.3%
weight lost at 80 weeks on 12 mg
45.3%
of people on 12 mg lost 30% or more
Jun 2026
Studies inside TRIUMPH-1
At the American Diabetes Association meeting, Lilly shared smaller studies run inside TRIUMPH-1. In people with obstructive sleep apnea, breathing pauses during sleep fell by up to 60.6%. In people with knee osteoarthritis, knee pain scores fell by up to 73.1%. 18
60.6%
fewer breathing pauses in sleep apnea, best group
Jul 2026
Two more Phase 3 trials
In TRIUMPH-2, 1,152 adults with type 2 diabetes and obesity or overweight lost 20.8% of their weight on 12 mg (placebo 4.0%), and A1c fell by up to 1.6 points. In TRIUMPH-3, 1,949 adults with severe obesity and heart or blood vessel disease lost 22.6% on 12 mg (placebo 3.2%). With these results in, Lilly said it plans to file with the FDA in early 2027. 11
20.8%
weight lost in TRIUMPH-2 on 12 mg
22.6%
weight lost in TRIUMPH-3 on 12 mg
Sep 2026
LatestLatest
TRIUMPH-1 was published in the New England Journal of Medicine and TRIUMPH-2 in The Lancet. Journals have outside experts check a study before they publish it. The papers lead with a stricter measure that counts everyone who started, including people who stopped the drug. By that measure, people on 12 mg in TRIUMPH-1 lost 25.0% of their weight, against 3.9% on placebo. 231
25.0%
weight lost on 12 mg, counting everyone who started (TRIUMPH-1)
Trial results
Pick a trial. The bars show average results for each dose and for placebo, on the same scale. The trials enrolled different people, so compare across trials with care.
Phase 3
Published in NEJM, September 2026Adults with obesity or overweight, without diabetes
Average weight lost by people who stayed on treatment. Placebo is a dummy shot with no drug.
| Arm | Result |
|---|---|
| 4 mg | 19.0% |
| 9 mg | 25.9% |
| 12 mg | 28.3% |
| Placebo | 2.2% |
Side effects
The most common side effects were stomach and gut effects like nausea. The bars compare the highest dose with placebo.
Nausea
TRIUMPH-1 · 12 mg
On 12 mg, nausea was almost three times as common as on placebo.
Stopped because of side effects
TRIUMPH-1 · 12 mg
About 1 in 9 people on 12 mg stopped the drug because of side effects.
Stopped because of side effects
TRIUMPH-4 · 12 mg
On 9 mg, 12.2% stopped because of side effects.
Dysesthesia (unusual skin feeling)
TRIUMPH-4 · 12 mg
A feeling like tingling or extra skin sensitivity. On 9 mg it was 8.8%. This is not common with older GLP-1 drugs.
What’s next
Results still to come, and the steps before retatrutide could be prescribed. Dates marked “estimated” come from trial listings on ClinicalTrials.gov and can move.
TRANSCEND-T2D-2 compares retatrutide with semaglutide in about 1,250 adults with type 2 diabetes. Its main data collection was listed to finish in August 2026.
TRANSCEND-T2D-3 is testing retatrutide in about 320 adults with type 2 diabetes and moderate or severe kidney disease.
TRIUMPH-5 compares retatrutide with tirzepatide (Mounjaro, Zepbound) in about 800 adults. Until it reports, every comparison between the two comes from separate trials.
Lilly says it plans to send the FDA an application for approval in the first quarter of 2027. The FDA then reviews the data before it decides. Until the FDA approves it, retatrutide isn’t available as a prescription medicine.
Further trials are studying keeping weight off over time (TRIUMPH-6) and chronic low back pain (TRIUMPH-7), among others.
TRIUMPH-OUTCOMES follows about 10,000 people to learn whether retatrutide lowers the risk of heart and kidney problems over time.
No. Retatrutide is not FDA-approved and isn’t available as a prescription medicine. Lilly says it plans to ask the FDA for approval in the first quarter of 2027.
Sources: Retatrutide TRIUMPH-2 results presented at EASD 2026, FDA's concerns with unapproved GLP-1 drugs used for weight loss
No one knows yet. Lilly plans to file in early 2027, and the FDA reviews an application before it decides. Lilly has not given a date for a decision.
Sources: Retatrutide TRIUMPH-2 results presented at EASD 2026
In TRIUMPH-1, people on the highest dose (12 mg) who stayed on treatment lost 28.3% of their body weight on average after 80 weeks, against 2.2% on placebo. Counting everyone who started, including people who stopped, it was 25.0% against 3.9%. These are averages, not what any one person can expect.
Sources: Retatrutide in the TRIUMPH-1 obesity trial, Retatrutide, a Triple Hormone Receptor Agonist, for Treatment of Obesity (TRIUMPH-1)
The most common were stomach and gut effects such as nausea. In TRIUMPH-1, 42.4% of people on 12 mg had nausea, against 14.8% on placebo. Some people also had dysesthesia, an unusual skin feeling such as tingling.
Sources: Retatrutide in the TRIUMPH-1 obesity trial, Retatrutide in the TRIUMPH-4 knee osteoarthritis trial
Tirzepatide acts on two hormone receptors, GIP and GLP-1. Retatrutide acts on those two plus a third, glucagon. A trial comparing them directly, TRIUMPH-5, has not shared results yet.
Sources: Zepbound (tirzepatide) US Prescribing Information, LY3437943, a novel triple glucagon, GIP, and GLP-1 receptor agonist for glycemic control and weight loss: from discovery to clinical proof of concept, TRIUMPH-5: retatrutide compared with tirzepatide (NCT06662383)
Some studies may still be looking for people. You can search ClinicalTrials.gov for retatrutide and ask a doctor whether a study might fit you.
Sources: Retatrutide studies
No. The FDA says retatrutide can’t be used in compounding under federal law and has not been found safe and effective for any condition. It has warned companies that sell retatrutide labeled for research use.
Sources: FDA's concerns with unapproved GLP-1 drugs used for weight loss
Trial dose math, the calculators for approved medicines, and common mistakes.
All guidesThe medical and device facts on this page come from these sources. Each entry shows the date we accessed it.