How to read a Certificate of Analysis (COA)
By Greg Huang
Founder of multiple consumer brands in the dietary supplement and nutrition industry since 2009 · Reviewed by Dr. James Pendleton, ND, licensed primary care physician, 20+ years in naturopathic medicine
Last verified April 25, 2026Published April 25, 2026
Definition
A Certificate of Analysis is a batch-specific lab document that states what an ingredient or finished supplement actually contains, tested against a written specification. Under 21 CFR §111.75, contract manufacturers must verify the identity of every incoming dietary ingredient. The COA is the artifact that proves they did. Bad COAs share three telltales: missing method IDs, missing specification limits, and missing lab accreditation.
§1What a COA must contain
Direct answer: seven fields. Five are required.
| Field | Required? | Bad-COA tell |
|---|---|---|
| Batch / lot number | Required | Generic placeholder |
| Manufacturing date | Required | Missing or in future |
| Test method (e.g., HPLC, HPTLC) | Required | Method blank or 'in-house' |
| Specification limit per analyte | Required | Pass/fail without limit |
| Result per analyte | Required | Range without value |
| Lab accreditation (ISO 17025) | Strong signal | No accreditation listed |
| Analyst signature | Standard | Unsigned PDF |
A COA without a method ID is functionally a guess. If a lab does not say how they tested for vitamin D3, you do not know whether they ran HPLC (gold standard) or a colorimetric assay (which can mistake other compounds for D3).
Method ID example: USP <2232> is the dietary-supplements elemental-contaminants chapter. A COA that says "Heavy Metals: pass" without a method ID does not let you confirm the lab actually ran <2232> rather than a less rigorous in-house screen.