How to Read a Certificate of Analysis: A Buyer’s Framework

A Certificate of Analysis (CoA) is one of the most useful documents a supplement buyer can request — and one of the least understood. Here’s how to actually read one.

What a CoA Is

A Certificate of Analysis is a lab document verifying what’s actually in a specific batch of a product — the results of testing performed on that batch, not a generic claim about the product line in general. A legitimate CoA is batch-specific, meaning it corresponds to a particular lot number, not a one-time test used to represent every future batch.

The Sections Worth Checking

• Identity testing — confirms the product actually contains what it claims to contain (verifying the ingredient itself, not just measuring a quantity).
• Potency/quantity results — the measured amount of active ingredient compared to the label claim, usually expressed as a percentage of label claim.
• Contaminant testing — heavy metals (lead, arsenic, cadmium, mercury), microbial testing, and, where relevant, pesticide residue testing.
• Testing lab name and accreditation — a legitimate CoA names the actual lab that performed the testing, ideally one with ISO 17025 accreditation.
• Lot number and test date — ties the document to a specific manufacturing batch, not a generic template.

Red Flags to Watch For

A CoA with no lot number, no named testing lab, a test date far removed from the product’s manufacture date, or one that only shows a subset of the sections above (commonly just potency, skipping contaminant testing) is worth questioning. Some brands will show a CoA for one product and imply it represents their whole line — that’s not how legitimate batch testing works.

How to Request One

A manufacturer confident in its testing practices should be able to provide a current CoA for the specific product and lot you’re purchasing on request. Sierra Life Sciences manufactures under 21 CFR Part 111 cGMP compliance at our Santa Rosa, California facility, with batch-level testing documentation available for our products.