GLP-1 & weight loss · Evidence comparison
Tirzepatide vs Retatrutide
The most-searched 'next-generation' weight-loss question: the approved dual-agonist tirzepatide versus the investigational triple-agonist retatrutide.
Tirzepatide
Retatrutide
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
Tirzepatide
Evidence grades
Metabolic / weight loss
Retatrutide
Evidence grades
Regulatory status at a glance
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.
Retatrutide
Investigational. NOT approved by the FDA, EMA, or any major regulator as of mid-2026; in Phase 3 (Lilly's TRIUMPH program), with a regulatory filing anticipated around late 2026 at the earliest. Per Lilly, legally available only to clinical-trial participants. No legal prescription or compounding pathway exists; anything sold online as 'retatrutide' is unapproved gray-market product.
Key differences
- Tirzepatide is FDA-approved and prescribable; retatrutide is investigational and, per Lilly, legally available only to clinical-trial participants.
- Both weight-loss claims are graded S+, but retatrutide's rests on Phase 2 data plus meta-analysis while tirzepatide has a full Phase 3 program and years of approved use.
- Retatrutide activates three receptors (glucagon, GIP, GLP-1) and has produced the largest trial weight loss reported to date; its Phase 3 program (TRIUMPH) is ongoing.
- Anything sold online as 'retatrutide' or as 'research' tirzepatide is unapproved gray-market material, graded C.
The bottom line
Tirzepatide is a proven, approved option; retatrutide is the more powerful-looking but still-investigational one you cannot legally obtain outside a trial. Both weight-loss claims sit at S+, but retatrutide's is built on earlier-stage evidence. We don't recommend either — we grade the evidence and flag that only one is an approved medicine.
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
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.
Full evidence brief
Retatrutide →
An investigational Eli Lilly injectable that activates three gut/metabolic hormone receptors at once and has produced the largest weight loss yet seen in obesity trials — but is not approved or legally available outside clinical trials.
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