Methodology
How we grade peptide vendors
Our shared assessment combines lab results, evidence confidence and reviewed business signals. Lab scoring includes purity, quantity, identity and contamination findings. Affiliate payments never affect a grade or ranking.
Where the test results come from
Results come from independent lab testing of vials sent in by members of the public, bought by an independent tester, or sent by the shops themselves. We copy each published measurement with its lab, batch number and test date, and grade it ourselves; nobody else's rating is used.
Every test on a vendor review links to its original lab report. If a number looks wrong, check it at the source.
Lab reports a shop publishes itself count at 50% weight and earn no independence credit: the shop chooses which batch to send and which report to publish, so they can't tell you what a random order contains.
What each test measures
- Identity
- Is the compound in the vial the one on the label? A failed identity test means the sample was something else, or nothing measurable.
- Purity
- What share of the sample is the labelled peptide, usually measured by HPLC. Research listings commonly claim 98–99% or higher.
- Quantity
- How many milligrams were actually in the vial compared with the amount printed on it. A 10 mg vial holding 7.8 mg is a 78% fill.
Test results, A to F
Each vial scores out of 100: half for purity (full marks at 99.5% or higher, zero at 90%), half for how close it was to the dose on the label (full marks within ±5%, zero beyond ±50%). A wrong peptide scores zero and costs the shop a further 1.5 points for every 1% of vials affected. A vial that tests positive for bacterial toxins scores no more than 30.
A shop's grade, overall or for one peptide, is the average of its vials, with recent vials counting more (weight halves every 365 days). With only a few vials the score is pulled toward a typical result, so one perfect vial can't earn an A.
| Grade | Score | Reads as |
|---|---|---|
| A | 90 or higher | Vials were the right peptide, very pure and close to the labelled dose. |
| B | 80 to 89.9 | Mostly good results, with some measurements off target. |
| C | 70 to 79.9 | Results were mixed: some measurements missed the mark. |
| D | 60 to 69.9 | Results often had problems with purity, dose or identity. |
| F | below 60 | Results often failed: wrong peptide, low purity or far-off doses. |
A vial passes our basic check if it's the right peptide, at least 99.5% pure and within 35% of the labelled dose. “Filled to label” means no more than 5% under.
Strength of evidence and shop reputation
Strength of evidence scores out of 100 how far the results can be trusted: how many vials were tested (up to 35), who sourced them (up to 20: full credit when the tester bought the vial like a customer, 75% when a buyer sent it in anonymously, none when the shop chose it), batch numbers, how recent the tests are, lab reports you can check, contamination tests and more than one lab. A 80+, B 70+, C 60+, D 50+, F 0+. Updated October 27, 2026: anonymous buyer submissions now count 75% (was 40%), and a lab report you can check counts in full.
Shop reputation starts at 100; each problem we can source costs points (critical 35, major 20, minor 7). It shows as not reviewed until we have checked, and then doesn't count.
The verdict weights test results 45%, evidence 25% and reputation 30%. It can't be higher than the test-results grade (strong evidence makes results more reliable, not better), or higher than D if the shop can't be ordered from or its test results fail. A shop with no lab results gets no grade and isn't recommended. A: grade a; B: grade b; C: grade c; D: grade d; F: grade f.
What a grade can't tell you
- It describes tested batches. A new batch can be better or worse, so check the test dates.
- It isn't a verdict on the business. Shipping, payment safety and customer service aren't measured in a lab. Our vendor verification checklist covers those.
- No tests means no grade. An ungraded vendor isn't proven bad, but no analytical result can be inferred. Grades are not vendor recommendations.
Partners and independence
Every quality list uses the same order: active vendors first, then composite grade, score, sample count and vendor slug to break ties. Peptide comparisons use peptide-specific lab and evidence results with vendor-wide business signals. A quality leader does not need a price listing.
Best value is the lowest recorded listing $/mg among the top 25% of active, graded vendors, rounded up before looking at prices. Missing prices never widen that pool. Lowest price is the minimum recorded USD listing $/mg, independent of grade, stock or age. Check the listing date and stock; estimates never win offer picks.
Some vendor links are affiliate links, and partners are labelled on their reviews. A partnership never changes a test result or a grade, and vendors can't pay for one.
When a review suggests a better-tested shop for a peptide, the shop must be graded A or B for that peptide on at least 3 vials it didn't choose, tested in the last year, and be open. Among shops that pass, the shared quality ranking decides the order, never partner status.
Who runs Peptide Vendor Reviews and how it makes money is on the about page.