Online Certificates of Analysis for Peptides: What They Do and Do Not Show
What a certificate of analysis is, what a purity percentage can and cannot tell you, and what studies and FDA say about peptide products sold with test reports.
Content last updated . This page has not been medically reviewed.
Quick answer
A certificate of analysis (COA) is a report from a laboratory or manufacturer listing the tests run on a batch of a substance and the results. It can be useful inside a regulated supply chain. A COA posted on a seller's website does not establish that the product in a particular vial is the labeled peptide, in the labeled amount, sterile, free of endotoxin, or safe to inject. This page is information only. It does not offer a way to "verify" an injectable at home, and nothing here is a checklist for deciding a product is safe.
Evidence labels used: marketing claim (a seller's statement), evidence of harm, insufficient evidence.
Where COAs have a defined role
Under US pharmacy compounding law, FDA says bulk drug substances must be accompanied by a valid certificate of analysis and must come from an establishment registered with FDA, and it urges compounders to know their bulks supplier. [1] Here the COA is one document among several requirements, held by a licensed pharmacy that is itself regulated. It is not a consumer safety label, and it does not make a compounded drug FDA approved. [2]What a purity percentage does not answer
A figure such as "99% purity" usually describes one measurement of one sample. Several different questions sit behind a vial of injectable peptide:| Question | Does a purity figure answer it? |
|---|---|
| Is this the exact molecule named on the label? | Not by itself. Naming can be ambiguous (see below). |
| Is the amount per vial what the label says? | No. A purity figure is a fraction, not a quantity. |
| Are there peptide-related impurities or aggregates? | Only if the report tests for them. FDA's list of substances with possible safety risks cites impurities, aggregation and immunogenicity risk for several promoted peptides. [3] |
| Are there metals or leftover solvents? | Only if tested; the Belgian study found arsenic and lead in falsified peptide drugs. [4] |
| Is it sterile and free of endotoxin? | No; these need separate tests. |
| Is it the same material in your vial as in the tested batch? | No; a report cannot show that. |
What testing studies found
In a 2024 study of semaglutide vials bought from illegal online pharmacies, measured purity ranged from 7.7% to 14.37% against a 99% claim on the labels, content exceeded the labeled amount by 28.56% to 38.69%, and endotoxin was detected in all samples. [5] That is three vials from one product class, so it cannot be generalized to every seller. But it is a documented case where a label claim and independent laboratory results differed widely. A 2018 study of ten commonly falsified peptide drugs found purity between 5% and 75% for cysteine-containing peptides and toxic elements in some samples. [4]Names versus molecules
A product name is not a molecular identity. FDA's list describes the substance sold as TB-500 as thymosin beta-4 fragment LKKTETQ, not the full thymosin beta-4 protein. [3] A published veterinary doping-control paper describes a preparation called TB-500 whose key ingredient is the peptide LKKTETQ with an acetylated N-terminus. [6] A COA that says "TB-500" therefore needs to state exactly which molecule was tested. See Research Peptide Naming and Identity Problems."Third-party tested" and "research use only"
"Third-party tested" is a marketing claim unless you know who tested what, on which batch, with which method, and whether the lab was independent of the seller. We found no regulator page that endorses consumer-facing COAs as proof of injection safety, and we did not search beyond FDA, WHO and PubMed. FDA has also said that "Research Use Only" wording does not change the status of a product when a seller's website shows it is meant for human use. [7]Better questions to ask a clinician
These are not tests of a product. They are questions for a licensed prescriber or state-licensed pharmacist: Is this an FDA-approved medicine, a compounded medicine, or neither? Which pharmacy prepared it? Why is an approved medicine not suitable? See Approved, Investigational and Unapproved Peptides and Mislabeling, Incorrect Strength and Degradation Products. If you feel unwell after an injection, seek care; in the US call 911 in an emergency or Poison Help at 1-800-222-1222.Frequently asked questions
Does a certificate of analysis prove a peptide is safe to inject?
No. It reports specific tests on a specific batch. Sterility, endotoxin and identity are separate questions, and the report cannot show that your vial matches the tested one.
What does "99% purity" mean?
Generally the proportion measured as the main component in one analysis. In a 2024 study, vials claiming 99% measured 7.7% to 14.37%. [5]
Do pharmacies use COAs?
Under FDA's 503A framework, bulk drug substances must be accompanied by a valid COA and made by an FDA-registered establishment. [1]
Is "third-party tested" the same as FDA approved?
No. FDA says compounded drugs are not FDA approved and are not reviewed for safety, effectiveness or quality before marketing. [2]
Can I use a COA to decide whether to buy a peptide?
This site does not give buying advice. Regulators advise obtaining prescription medicines through licensed pharmacies. [2]
References
- U.S. Food and Drug Administration, Bulk Drug Substances Used in Compounding Under Section 503A of the FD&C Act. Read 2026-10-22.
- U.S. Food and Drug Administration, FDA's Concerns with Unapproved GLP-1 Drugs Used for Weight Loss (content current as of 10/01/2026). Read 2026-10-22.
- U.S. Food and Drug Administration, Certain Bulk Drug Substances for Use in Compounding that May Present Significant Safety Risks (content current as of 04/22/2026). Read 2026-10-22.
- Impurity profiling of the most frequently encountered falsified polypeptide drugs on the Belgian market, Talanta 2018. Read 2026-10-22 (abstract).
- Multifactor quality and safety analysis of semaglutide products sold by online sellers without a prescription, J Med Internet Res 2024. Read 2026-10-22 (abstract).
- Doping control analysis of TB-500, a synthetic version of an active region of thymosin beta-4, in equine urine and plasma by LC-MS, J Chromatogr A 2012. Read 2026-10-22 (abstract).
- U.S. Food and Drug Administration, Warning Letter to Gram Peptides (721806), 03/31/2026. Read 2026-10-22.
Education, not medical advice. This page is for general information. It does not diagnose or treat any condition and is not a substitute for care from a qualified health professional. Natural does not automatically mean safe. Ask a clinician or pharmacist before changing your care, especially if you take medication, are pregnant or breastfeeding, or have a health condition.