Short answer
A COA reports test results for one batch from one lab. It is only as reliable as the lab and the chain of custody behind it, and it says nothing about the batch in your hands unless the batch numbers match.
Start with the batch, not the brand
A COA applies to one specific batch. Match the lot number on the document to the vial you actually received: a certificate for a different batch only describes that batch.
Identity before purity
The first question is whether the vial contains the right molecule at all, which mass spectrometry or sequencing answers. A 99 percent purity figure for the wrong compound is worthless.
What HPLC and MS each tell you
HPLC estimates purity by comparing peak areas; mass spectrometry confirms molecular weight and identity. A COA showing only one of the two leaves a gap worth asking about.
What purity numbers leave out
Standard purity assays do not cover sterility, endotoxin, aggregation, residual solvents, or concentration accuracy. For injectable products those are common failure points, and endotoxin requires its own test.
Who ran the test
An in-house COA is a marketing document; a third-party report from an identifiable, accredited lab carries more weight. Check the lab name, the method, the date, and whether the report can be verified with the lab directly.
Red flags worth walking away from
Missing batch numbers, the same COA reused across a whole product line, no identifiable lab, purity claims with no method stated, and certificates that exist only as images on a seller's page.
Sources
- 1.
FDA. Certain Bulk Drug Substances for Use in Compounding that May Present Significant Safety Risks 2026.
Accessed 2026-06-08.
FDA summarizes potential significant safety risks and missing safety information for several nominated peptide bulk substances.
- 2.
FDA. FDA to Compounders: Know Your Bulks and Excipients Suppliers 2026.
Accessed 2026-06-09.
FDA supplier-quality guidance for compounders; used for product-quality context, not as evidence of NAD+ efficacy or route instructions.