Approved drug (Ozempic / Wegovy) with large randomised trials — figures below are from those trials, not from research-grade vials
Semaglutide has one of the best-characterised safety profiles of any compound on this site because it is an approved medicine studied in tens of thousands of trial participants. The dominant adverse effects are gastrointestinal and dose-related. None of that data was generated with research-grade vials, whose identity and dose are not verified by any regulator.
Research-use information only. Research-grade Semaglutide 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 | 44.2% vs 17.0% placebo | Most frequent during dose escalation; mostly mild-to-moderate. | STEP 1, Wilding et al. 2021 |
| Diarrhoea | 31.5% vs 15.9% | Typically transient. | STEP 1 |
| Vomiting | 24.8% vs 6.6% | Dose-related. | STEP 1 |
| Constipation | 23.4% vs 9.5% | — | STEP 1 |
| Discontinuation for GI events | 4.5% vs 0.8% | — | STEP 1 |
| Gallbladder events, pancreatitis | not quantified | Uncommon but recognised class risks carried on the label. | Wegovy prescribing information |
| Diabetic retinopathy complications | not quantified | Signal seen in SUSTAIN-6 in people with diabetes and pre-existing retinopathy. | Marso et al. 2016 |
Regulatory status: FDA-approved as Ozempic (T2D, 2017) and Wegovy (chronic weight management, 2021). Research-grade semaglutide is not approved for any use.
Everything above describes Semaglutide the molecule. The risk specific to a research vial is different: it may not contain Semaglutide 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 Semaglutide so far.
9 of the 77 vendors on our scoreboard list Semaglutide with a price we read on the product page (5 Sept 2026–2 Oct 2026). Of those, 8 name their testing laboratory, 8 publish certificates that resolve on the lab's own site, and 8 publish measured milligrams against the label. The full ranking, with every dated price, is on Best Semaglutide Vendors.
| Vendor | Rubric | Lab named | Price read |
|---|---|---|---|
| Peptide Giantspartner | 10/10 | Janoshik Analytical · Vanguard Laboratory | $32.00 · 5mg · 2 Oct 2026 |
| Purgo Labspartner | 10/10 | SteriGenix · Freedom Diagnostics | $49.99 · 10mg · 2 Oct 2026 |
| Amino Clubpartner | 9/10 | ILS Labs | $49.99 · 10mg · 2 Oct 2026 |
| PeakForce Labs | 8/10 | Freedom Diagnostics (on certificates) | $69.00 · 10mg · 2 Oct 2026 |
| PS Peptidespartner | 8/10 | North American Diagnostics | $64.99 · 10mg · 2 Oct 2026 |
Top 5 by rubric score; 4 more on the ranking page.
1 certificate for Semaglutide in the COA library: 0 checkable on the laboratory's own site, 0 stating measured mass against the label, 1 carrying a flag.
The pharmacology is the same if the vial contains what it claims. The difference is that nobody has verified that: a research vial may be under- or over-dosed or misidentified, which changes the risk in ways no trial has measured. Our vendor pages show which sellers publish lab-verified net content.
In STEP 1 they clustered around dose-escalation steps and mostly resolved; a minority discontinued for GI reasons (4.5%).