Retatrutide

What is retatrutide?

Retatrutide is a synthetic peptide that acts together on the receptors of three gut-pancreas hormones involved in regulating blood sugar and appetite: glucose-dependent insulinotropic polypeptide (GIP), glucagon-like peptide-1 (GLP-1) and glucagon. ^[3] In this respect it differs from semaglutide and liraglutide, which act only on the GLP-1 receptor, and from tirzepatide, which acts on the GIP and GLP-1 receptors. General features of the class: GLP-1 agonists.

In published studies, retatrutide was administered subcutaneously once a week; it is being developed for obesity, type 2 diabetes and related conditions (knee osteoarthritis, sleep apnea). The TRIUMPH-2 paper describes the molecule as “currently under investigation” in these areas. ^[4] All of the phase 2 and phase 3 studies named below were funded by the manufacturer, and company employees were among their authors. ^{[1] [3] [4] [5]}

Is retatrutide approved? What is its status in Türkiye?

US: The FDA’s page on unapproved GLP-1 drugs (content current as of October 1, 2026) states that retatrutide cannot be used in compounded (pharmacy-prepared) drugs under federal law, is not a component of an approved drug, and has not been found safe and effective for any condition. The FDA reports that it has warned telehealth companies that market unapproved drugs such as retatrutide directly to consumers, active ingredient distributors that sell retatrutide and other GLP-1 active ingredients to drug compounders, and facilities that repackage retatrutide. ^[7]

Türkiye: There is no product containing retatrutide on the TİTCK (Turkish Medicines and Medical Devices Agency) List of Licensed Human Medicinal Products dated October 16, 2026. ^[8] Two provisions in the legislation are directly relevant:

• Article 3 of Law No. 1262 on Pharmaceutical and Medicinal Preparations (İspençiyari ve Tıbbi Müstahzarlar Kanunu) requires Ministry permission before domestically produced medicinal preparations are placed on the market and before those produced abroad are imported. ^[9]
• Article 24 of Law No. 6197 on Pharmacists and Pharmacies (Eczacılar ve Eczaneler Hakkında Kanun) provides that medicines cannot be sold on the internet or in any other electronic medium. ^[10]

Products sold online with the wording “for research purposes, not for human use” do not change this situation: according to the FDA, retatrutide is not a component of any approved drug, and these products do not undergo safety, efficacy and quality review before being sold. ^[7]

What did the phase 2 studies show?

• Obesity (NEJM, 2023): 338 adults with BMI ≥30, or 27–30 together with a weight-related disease, were followed for 48 weeks. At week 48, mean weight change was −8.7% in the lowest-dose group, −24.2% in the highest-dose group and −2.1% with placebo. In the highest-dose group, 83% of participants lost at least 15% of their body weight (2% with placebo). Gastrointestinal events were dose-dependent, mostly mild to moderate, and partly reduced with a lower starting dose; heart rate increased dose-dependently, peaked at week 24 and then decreased. ^[1]
• Type 2 diabetes (Lancet, 2023): In a placebo- and active comparator (dulaglutide)-controlled study of 281 people with type 2 diabetes in the US, HbA1c fell by 2.02 points in the highest-dose group and 1.41 points with dulaglutide at week 24 and did not change with placebo; weight loss at week 36 was 16.94% in the highest-dose group and 3.00% with placebo. Gastrointestinal adverse events were 35% in the retatrutide groups, 13% with placebo and 35% with dulaglutide; severe hypoglycemia and death were not reported. ^[2]
• Fatty liver (Nat Med, 2024): In the substudy of 98 obesity-study participants with liver fat of 10% or above, liver fat fell by a relative 82.4% in the highest-dose group at 24 weeks (rose 0.3% with placebo); in 86% of this group liver fat dropped to the normal limit (below 5%). The primary endpoint is the liver fat fraction measured by MRI; clinical events related to liver disease are not endpoints of this substudy. ^[6]

What did the phase 3 studies find?

In 2026, the results of three phase 3 studies were published in peer-reviewed journals. The weight percentages in the table come from the “treatment-regimen” analysis (intention-to-treat approach), which keeps those who stopped treatment in their own group. Dose groups are named here only as “low, medium, high.”

Three limits are important in reading these results. First, the knee pain and sleep apnea results come from subgroups within TRIUMPH-1; they are prespecified endpoints of the study but each is a single study. Second, weight loss in people with type 2 diabetes is markedly smaller than in those without diabetes. Third, the endpoints of these studies are weight, HbA1c, pain and apnea index; they were not designed to measure events such as heart attack, stroke or death. ^{[3] [4]}

Does weight loss come from fat or from muscle?

In large weight loss, how much of the loss comes from lean mass including muscle is a frequently asked question. For retatrutide the only data are from the body composition substudy of the phase 2 diabetes study. In this substudy, which included 189 participants but in which only 103 completed treatment and two DXA measurements, total fat mass at 36 weeks fell by 23.2% in the highest-dose group, 4.5% with placebo and 2.6% with dulaglutide. The authors conclude that the ratio of lean (including muscle) mass loss to total weight loss is similar to other obesity treatments; the numerical value of this ratio is not in the published abstract. All of the authors are employees of the manufacturer. ^[12] Muscle strength and physical function are not endpoints measured in this substudy.

Is the effect on cardiovascular risk known?

Not yet. In a post hoc analysis of two phase 2 studies, retatrutide was associated with a reduction in non-HDL cholesterol (up to 21.0% in people with diabetes, 26.9% in those without) and in apolipoprotein B; the inflammation marker high-sensitivity CRP fell significantly only in people with obesity without diabetes (54.8%). ^[13] These are blood markers; they do not show that events such as heart attack or stroke are reduced.

A cardiovascular-kidney outcomes study (TRIUMPH-Outcomes) to measure event outcomes is ongoing. The design paper of TRANSCEND-CKD, a phase 2b mechanism study examining the effect on kidney function in 146 people with chronic kidney disease, states that this study was planned to help interpret the findings in the outcomes study. ^[14]

Is retatrutide more effective than semaglutide or tirzepatide?

In the three published phase 3 studies (TRIUMPH-1, TRIUMPH-2, TRANSCEND-T2D-1), the comparison group is placebo. ^{[3] [4] [5]} Comparison with another GLP-1 drug was made only in the phase 2 diabetes study: compared with dulaglutide, the HbA1c reduction was significantly greater in the highest-dose arm and in a medium-to-high-dose arm, and weight reduction was significantly greater in all arms except the lowest dose. ^[2] Placing the averages of different studies side by side (for example, TRIUMPH-1 with separate studies of other drugs) is not a reliable comparison, because participant characteristics, duration and analysis method differ. For the evidence on licensed options: Tirzepatide, Semaglutide.

What are the safety signals of retatrutide?

The findings that stand out in the published studies are as follows; the numbers and unknowns are on the side effects page.

• Gastrointestinal complaints: The most common adverse events in all studies. In TRIUMPH-2, diarrhea was 27–34% in the retatrutide groups and 13% with placebo; nausea was 14–28% versus 8%. ^[4]
• Heart rate: In the phase 2 obesity study it increased dose-dependently and fell after peaking at week 24. ^[1]
• Dysesthesia (abnormal sensation in the skin) and low blood pressure: In TRIUMPH-2, dysesthesia was 4–7% in the retatrutide groups and 1% with placebo; hypotension was seen at 1–6% versus under 1%. ^[4]
• Discontinuation: In TRIUMPH-2, permanent discontinuation due to an adverse event or death was 12% at the medium dose, 8% at the high dose, 4% at the low dose and 5% with placebo. ^[4]

Why is retatrutide sold online risky?

The FDA states that unapproved GLP-1 products have not undergone review for safety, efficacy and quality and that this is risky for patients. ^[7]

A concrete measurement of this risk comes from Australia. In an accredited-laboratory analysis of three products sold as retatrutide with the same amount written on the label, retatrutide was detected in all three; however, the measured amount was 51.3%, 165% and 190% of the label value. Heavy metals were at low levels; sterility and endotoxin were not tested. The authors state that only three samples were examined and the results may not represent the entire illicit market. One of the authors is linked to the community-based drug-checking service that performed the analysis. ^[11]

According to the authors, this means that users may unknowingly administer a markedly lower or higher amount than intended. ^[11] The safety findings in the phase 3 studies were obtained in adults selected by entry criteria and under a study protocol. ^[4]

Limits of this guide

This page summarizes published peer-reviewed studies and statements of regulatory bodies on retatrutide. It contains no dose, administration, storage or sourcing information and does not recommend use under any circumstances. The dose groups in the studies are referred to only as low, medium and high. When the licensing application and approval process for retatrutide is completed, the product information may contain limits different from the study results on this page.