Semaglutide vs Tirzepatide
It is the shot behind Ozempic and Wegovy, used for diabetes and weight loss. Trials in tens of thousands of people show about 15% weight loss and fewer heart attacks. It is the weekly shot behind Mounjaro and Zepbound, used for diabetes and weight loss. Large trials show 15% to 21% weight loss.
Both sit at grade A: strong human evidence. Both are FDA approved.
Evidence
AStrong human evidence
AStrong human evidence
Human studies cited
Animal or cell studies cited
Why the grade
Semaglutide has one of the largest trial programs of any peptide: the STEP trials in obesity (STEP 1, 1,961 adults), the SUSTAIN trials in type 2 diabetes, SELECT (17,604 adults with cardiovascular disease and obesity, the largest), FLOW in kidney disease, and systematic reviews pooling tens of thousands of participants. Weight loss, glucose lowering and reductions in heart attack, stroke and kidney outcomes are all shown in randomized placebo-controlled trials. What remains open is what happens over decades and how to stop without regaining.
Tirzepatide's weight-loss use rests on the SURMOUNT program of randomized placebo-controlled trials, the largest being SURMOUNT-1 with 2,539 adults, plus trials in type 2 diabetes, sleep apnea, weight maintenance and diabetes prevention. Every approved indication was granted on randomized data, so it grades A.
FDA
FDA approved
Semaglutide is FDA-approved as Ozempic (weekly injection, type 2 diabetes, 2017; with later indications to reduce cardiovascular events and, since January 2025, kidney disease progression in type 2 diabetes), Rybelsus (daily tablet, type 2 diabetes, 2019), and Wegovy (weekly injection, chronic weight management, 2021; cardiovascular risk reduction in obesity, 2024; MASH with liver fibrosis, 2025; an oral Wegovy tablet, December 2025). Compounded semaglutide is not FDA-approved.
FDA approved
Tirzepatide is approved by the FDA as Mounjaro (2022) for type 2 diabetes in adults, extended to children 10 and older and to cardiovascular risk reduction in adults with type 2 diabetes and established cardiovascular disease, and as Zepbound (2023) for chronic weight management and for moderate to severe obstructive sleep apnea in adults with obesity.
Sold for
Semaglutide is the GLP-1 injection behind Ozempic and Wegovy, the most talked-about weight loss drug of the decade.
Tirzepatide is the weight-loss injection that outperformed semaglutide, cutting body weight by about a fifth in trials.
Studies say
Randomized trials in tens of thousands of people show about 15 percent weight loss, roughly a 1 to 2 point HbA1c reduction, a 20 percent cut in major cardiovascular events and slower kidney decline, with gastrointestinal side effects and weight regain after stopping as the main caveats.
Multiple large randomized trials show weight loss of 15 to 21 percent, better glucose control than other diabetes drugs, and improvement in sleep apnea, with weight regain after stopping, which is a clean A.
Class
GLP-1 receptor agonist
Dual GIP + GLP-1 receptor agonist
Route
Several routes
Injection