Approved drug (Mounjaro / Zepbound) with large randomised trials — figures are from those trials
Tirzepatide's adverse-effect profile comes from the SURMOUNT and SURPASS programmes and is dominated by dose-related gastrointestinal effects, similar in kind to semaglutide. Research-grade tirzepatide is not the approved product and carries the additional, unmeasured risk of unverified identity and dose.
Research-use information only. Research-grade Tirzepatide is not an approved medicine; where trial or label figures appear below they belong to the pharmaceutical product studied, not to any research vial. This page does not give dosing or medical advice.
Every rate carries its source. Where no source exists, no rate is printed.
| Effect | Rate (sourced) | Detail | Source |
|---|---|---|---|
| Nausea | 24.6–33.3% (5–15 mg) vs 9.5% placebo | Mostly during escalation. | SURMOUNT-1, Jastreboff et al. 2022 |
| Diarrhoea | 18.7–23.0% vs 7.3% | — | SURMOUNT-1 |
| Vomiting | 8.3–12.2% vs 1.7% | — | SURMOUNT-1 |
| Constipation | 11.7–17.1% vs 5.8% | — | SURMOUNT-1 |
| Discontinuation for adverse events | 4.3–7.1% vs 2.6% | — | SURMOUNT-1 |
Regulatory status: FDA-approved as Mounjaro (2022) and Zepbound (2023). Research-grade tirzepatide is not approved for any use.
Everything above describes Tirzepatide the molecule. The risk specific to a research vial is different: it may not contain Tirzepatide at the labelled amount, and it may contain what the synthesis left behind. Identity (mass spectrometry), purity (HPLC), measured net content and an endotoxin result are the four lines on a certificate that bear on adverse effects, and only a certificate you can check at the laboratory tells you any of them. This is what we have verified for Tirzepatide so far.
12 of the 77 vendors on our scoreboard list Tirzepatide with a price we read on the product page (5 Sept 2026–2 Oct 2026). Of those, 11 name their testing laboratory, 9 publish certificates that resolve on the lab's own site, and 11 publish measured milligrams against the label. The full ranking, with every dated price, is on Best Tirzepatide Vendors.
| Vendor | Rubric | Lab named | Price read |
|---|---|---|---|
| Peptide Giantspartner | 10/10 | Janoshik Analytical · Vanguard Laboratory | $39.99 · 10mg · 2 Oct 2026 |
| Purgo Labspartner | 10/10 | SteriGenix · Freedom Diagnostics | $49.99 · 10mg · 2 Oct 2026 |
| Amino Clubpartner | 9/10 | ILS Labs | $59.99 · 30mg · 2 Oct 2026 |
| Idun Peptides | 9/10 | Kovera Labs (named in certificate captions only) | $24.99 · 10mg · 5 Sept 2026 |
| PeakForce Labs | 8/10 | Freedom Diagnostics (on certificates) | $129.00 · 30mg · 2 Oct 2026 |
Top 5 by rubric score; 7 more on the ranking page.
1 certificate for Tirzepatide in the COA library: 0 checkable on the laboratory's own site, 0 stating measured mass against the label, 1 carrying a flag.
Head-to-head tolerability has not been the primary endpoint of a trial; in separate trials the GI rates look broadly similar in kind, with tirzepatide's nausea rate somewhat lower at comparable efficacy. Individual response varies more than the averages.