Retatrutide vs Liraglutide
A weekly weight-loss injection not yet approved. In a large trial people lost up to a quarter of their body weight in 80 weeks. It is a daily injection for type 2 diabetes and for weight loss. Large trials of 9,340 and 3,731 people showed fewer heart problems and about 8% weight loss.
Both sit at grade A: strong human evidence. Retatrutide: In clinical trials. Liraglutide: FDA approved.
Evidence
AStrong human evidence
AStrong human evidence
Human studies cited
Animal or cell studies cited
Why the grade
There are two published phase 3 trials. TRIUMPH-1 randomized 2,339 adults with obesity and no diabetes for 80 weeks. TRIUMPH-2 randomized 1,152 adults with obesity and type 2 diabetes for 80 weeks. Behind them sit a 338-adult randomized phase 2 trial and its 98-person liver fat substudy. Several large randomized trials support the weight-loss use, which meets the A definition. What is missing is FDA approval, a trial run by anyone other than Eli Lilly, and safety data beyond 80 weeks.
Both uses rest on large randomized placebo-controlled trials: LEADER (9,340 patients with type 2 diabetes, cardiovascular outcomes) and the SCALE obesity trial (3,731 adults, 56 weeks of weight loss). Multiple other phase 3 trials sit behind the labels. What the citations do not cover is how liraglutide compares with the newer weekly GLP-1 drugs, which outperform it on weight.
FDA
In clinical trials
Retatrutide is an investigational drug and is not approved by the FDA for any use. Eli Lilly has said it plans to file for approval in the first quarter of 2027 after completing manufacturing data. Vials sold online as retatrutide are not a legal product; the FDA has stated that unapproved GLP-1 class drugs cannot be used in compounding.
FDA approved
Approved. Liraglutide is sold as Victoza (approved 2010) for type 2 diabetes in adults and children aged 10 and older and to reduce major cardiovascular events in adults with type 2 diabetes and heart disease, and as Saxenda (approved 2014) for chronic weight management in adults and adolescents aged 12 and older. Generic liraglutide for both indications has been approved since December 2024 and August 2025.
Sold for
Retatrutide is talked about as the next step beyond tirzepatide, a triple-hormone injection that produced the largest weight loss yet seen in a drug trial.
Liraglutide was the first daily GLP-1 drug to be approved for weight loss and is now marketed as the cheaper generic alternative to semaglutide for people who want a GLP-1 but cannot get or afford the newer ones.
Studies say
Two published phase 3 trials show about a quarter of body weight lost over 80 weeks in adults without diabetes and about a fifth in people with diabetes, with gut side effects, heart rate increases and abnormal skin sensations, which supports an A even though the drug is not approved.
Trials in nearly 10,000 diabetic patients and 3,700 adults with obesity showed fewer heart events and about 8 percent body weight loss respectively, which earns an A for both approved uses.
Class
Triple GLP-1 / GIP / glucagon agonist
GLP-1 receptor agonist
Route
Injection
Injection