PeptideChecked FAQ: Vendors, Testing, Codes and Legal Status

PeptideChecked is an independent site that rates research peptide vendors on how much evidence they publish about what they sell: certificates of analysis, named labs, independent test data, labeling and FDA record. We don't sell peptides and don't cover dosing or human use. Our full method is on the about page.

No. We don't buy or test products. Every rating is based on public documentation: vendor COAs, independent Finnrick data, FDA records and cited third-party reviews.

Through affiliate links. If you buy after clicking a link on our site, the vendor may pay us a commission at no extra cost to you. Partnerships can affect which vendors we feature and the order of our list, but never a vendor's rating. See our affiliate disclosure.

The order is our editors' pick. It weighs the rating together with other factors, including partnership terms. The rating shown next to each vendor is the one to use if you want the transparency score alone.

We re-check vendor facts, codes and prices regularly and date-stamp them on each page. Our peptide regulatory news tracker is updated monthly.

Use our contact page. We read corrections from readers and vendors, and we update pages when we can verify a change.

On our method, Peptide Plugs and NextGenPeps score highest because they name their testing labs on their own sites. Peptide Plugs also gives accession codes you can check on the lab's search. See third-party tested peptides for all eight, or the full best peptide vendors in the USA ranking.

Yes, for three vendors as of September 28, 2026: CHECKED for 10% off at PSPeptides, AFFILIATE50OFF for 50% off a first order at Ascension Peptides, and Affiliate5 for 5% off at Licensed Peptides. Vendors set the terms and can change them, so check the total at checkout. All codes are on our peptide coupon codes page.

More vendor questions are answered in our reviews, comparisons and use-case lists such as the cheapest peptide vendors and fastest shipping peptide vendors.

A certificate of analysis is a lab report for a specific batch. For peptides it usually shows purity by HPLC and identity by mass spectrometry. It's only useful if it names the lab, matches the lot number on your vial and can be verified with the lab. Read how to read a peptide COA or use our COA checklist.

Finnrick is an independent service that publishes test results for peptide samples bought from vendors, and rates vendors on them. As of our September 26-28, 2026 checks, only one of our eight listed vendors, Swiss Chems, had Finnrick test data. See what is Finnrick and our vendor testing tracker.

For what the purity number on a certificate actually measures, see HPLC purity explained.

It depends on the peptide and how it's sold. Most research peptides aren't controlled substances, but they aren't FDA-approved drugs either, and FDA acts against sellers whose marketing shows products are meant for people. A research-use-only label doesn't change that. Full details: are peptides legal?

No. Peptides sold for research use only are not approved by FDA for human or veterinary use. Approved peptide drugs, such as semaglutide, are legal only as prescription products. See FDA peptide regulation in 2026.

It converts the mass of peptide in a vial and the volume of bacteriostatic water added into a concentration, the volume that holds a target amount, syringe units on a U-100 or U-40 scale, and mcg per 0.1 mL. It's unit arithmetic only and runs in your browser. Open the peptide reconstitution calculator, or see all our tools.

A U-100 syringe has 100 units per mL and a U-40 syringe has 40, so the same 0.1 mL reads as 10 units on U-100 and 4 units on U-40. Always check the scale printed on the barrel. More in U-40 vs U-100 syringes.

Sterile water with 0.9% benzyl alcohol added as a preservative, which is why it's sold in multiple-use vials. Sterile water for injection has no preservative and is meant for a single use. See bacteriostatic water vs sterile water.

Still stuck on a term? Our research peptide glossary defines more than 50 of them.