GLP-1 & weight loss · Evidence comparison
Semaglutide vs Tirzepatide
The two FDA-approved injectables that dominate the weight-loss conversation — Ozempic/Wegovy versus Mounjaro/Zepbound. Here is how the trial evidence for each grades out, side by side.
Semaglutide
Tirzepatide
Headline claim shown. Grades are claim-specific — see the full breakdown below.
The evidence, side by side
Every graded claim from each brief. Grades are read straight from the source-checked briefs — one molecule can be strong for one use and weak for another.
Metabolic / weight loss
Semaglutide
Evidence grades
Metabolic / weight loss
Tirzepatide
Evidence grades
Regulatory status at a glance
Semaglutide
FDA-approved prescription drug — the only fully approved compound on this site so far. Approved as Ozempic (injection, type 2 diabetes, 2017), Rybelsus (oral, type 2 diabetes, 2019), and Wegovy (injection, chronic weight management, 2021); Wegovy gained a cardiovascular-risk-reduction indication in March 2024, and an oral Wegovy (semaglutide 25 mg) for weight management launched in the U.S. in January 2026. Carries an FDA boxed warning for thyroid C-cell tumors; contraindicated with a personal/family history of medullary thyroid carcinoma or MEN 2. The U.S. semaglutide shortage was declared resolved in February 2025, ending most legal compounding. Semaglutide sold online as a 'research chemical,' or compounded using unapproved salt forms, is not an FDA-approved product.
Tirzepatide
FDA-approved prescription drug and a dual GIP/GLP-1 receptor agonist. Approved as Mounjaro (injection, type 2 diabetes; May 2022) and Zepbound (injection, chronic weight management; November 2023); Zepbound also gained approval for moderate-to-severe obstructive sleep apnea in adults with obesity in December 2024 — the first medication ever approved for OSA. Carries an FDA boxed warning for thyroid C-cell tumors; contraindicated with a personal/family history of medullary thyroid carcinoma or MEN 2. The U.S. tirzepatide shortage was declared resolved in December 2024, ending most legal compounding. Tirzepatide sold online as a 'research chemical,' or compounded from unapproved sources, is not an FDA-approved product.
Key differences
- Both earn an S+ grade for weight loss on multiple large randomized trials — the strongest evidence tier on this site.
- Tirzepatide acts on two hormone receptors (GIP and GLP-1) to semaglutide's one, and produced greater weight loss than semaglutide in head-to-head trials.
- Each carries a different extra approval: tirzepatide (Zepbound) for obstructive sleep apnea, semaglutide (Wegovy) for cardiovascular-risk reduction.
- For both, the S+ grade applies only to the approved, prescribed drug — the 'research-grade' versions sold online are graded C and are not the trial drug.
The bottom line
Both reach the site's top evidence grade for weight loss, and tirzepatide showed the larger effect head-to-head — but each is approved for a different additional use, and those grades belong to the regulated prescription drug, not to anything sold online. We don't tell you which to use; we show what the evidence has earned each one. Which drug fits a given person is a conversation for a licensed prescriber.
PeptideIQ Base does not recommend, rank, or endorse any peptide, dose, or product. We grade the strength of the evidence so you can read it for yourself.
Read the full briefs
Full evidence brief
Semaglutide →
An FDA-approved GLP-1 medication (Ozempic, Wegovy, Rybelsus) with strong clinical-trial evidence for major weight loss and cardiovascular-risk reduction — but that evidence applies to the prescribed, regulated drug, not to the compounded or 'research-grade' semaglutide widely sold online.
Full evidence brief
Tirzepatide →
An FDA-approved dual GIP/GLP-1 'twincretin' (Mounjaro, Zepbound) that produces the largest weight loss of any approved obesity drug and beat semaglutide head-to-head — but that evidence belongs to the regulated, prescribed drug, not to the compounded or 'research-grade' tirzepatide widely sold online.
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