What Is a Certificate of Analysis?

Quick answer on certificates of analysis

A certificate of analysis, usually shortened to COA, is the laboratory document recording what was tested in a specific batch of a product, which methods were used, what the specification limits were, and what the results came back as. It is the evidence behind the phrase "third-party tested." Without one tied to the lot number on your bottle, that phrase is an assertion rather than a fact. Most brands will send you one if you ask. The ones that won't have told you something.

What a COA actually contains

A complete certificate has four things on it, and the fourth is the one people forget to look for.

The first is identification: the product name, the lot or batch number, and usually the date of manufacture. This is what ties the document to the bottle in your hand rather than to some other production run.

The second is the list of tests performed. Heavy metals, microbiological contaminants, identity, potency, residual solvents, pesticides — which of these appear depends on the material and on how seriously the manufacturer takes it.

The third is the result for each test, with units attached. Parts per million for heavy metals, colony-forming units per gram for microbials, a percentage for an active compound.

The fourth is the specification limit — the threshold the result was measured against — and the method used to measure it. A result without a limit beside it is a number floating in space. Knowing that lead came back at 0.01 ppm tells you nothing until you know whether the limit was 1 ppm or 0.005.

Raw material versus finished product

This distinction causes more confusion than any other, and it is worth getting straight.

A raw material COA covers the ingredient as it arrived at the manufacturer. It usually carries the identity test and the potency figure, because that is where those are established. An extract supplier will test their extract and issue a certificate for it.

A finished product COA covers the bottled product after manufacture. It is the one that tells you what is actually in the thing you bought, after blending, bottling and whatever else happened in between.

Both are useful and they answer different questions. A brand showing you only a raw material certificate is showing you what they bought, not what they sold you. We publish both stages for Logic, and we label which is which, because conflating them is the easiest way to make a testing programme look more thorough than it is.

Who issued it matters as much as what it says

A certificate issued by the manufacturer's own in-house laboratory is not third-party testing, however carefully the work was done. The phrase means an independent laboratory with no commercial interest in the result.

The stronger signal is an ISO 17025 accredited laboratory. That accreditation is an international standard for testing competence, assessed by an outside accreditation body, and it means the lab's methods and quality systems have been audited rather than asserted. If a brand names its laboratory, you can look it up. If it doesn't name the lab at all, that is itself an answer.

The same logic applies on the manufacturing side, which we unpack in how to choose a supplement brand.

How to read the numbers without a chemistry degree

You do not need to know what inductively coupled plasma mass spectrometry is to read a COA usefully. You need to do one thing: compare the result column to the specification column.

If the specification for lead is under 1 part per million and the result reads 0.01, the material came in a hundred times below the limit. If the result reads 0.9, it passed, but only just. Both are a pass. They are not the same thing, and only the actual numbers tell you which one you are holding.

This is why a certificate that reports only "Pass" or "Conforms" without the measured value is a weaker document. It is technically accurate and it withholds the only information that would let you judge for yourself.

Three questions worth asking

If you are evaluating a brand rather than a document, these three do most of the work.

Can you get a COA matched to the lot number printed on your bottle, rather than a generic example? Does it name the testing laboratory? And does it show measured values against specification limits rather than the word "pass"?

A brand that answers yes to all three is being genuinely transparent. A brand that answers yes to none of them may still be making a perfectly good product — but you have no way to know, and that is the entire point.

The related question of what a label can and cannot tell you is covered in how to read a mushroom supplement label, and the broader quality picture in what standardized extract actually means.

Frequently asked questions

What does COA stand for? Certificate of analysis. It is the laboratory document recording the tests performed on a specific batch, the methods used, the specification limits and the measured results.

How do I get a COA for a supplement I bought? Email the brand with the lot or batch number printed on the bottle or box. A brand with a real testing programme will send the certificate for that specific lot.

Is a COA proof that a supplement is safe? It is evidence about the specific things that were tested in a specific batch. It tells you nothing about tests that were not run, or about other lots. It is a document to read rather than a guarantee to accept.

What is the difference between a raw material COA and a finished product COA? A raw material COA covers the ingredient as received by the manufacturer. A finished product COA covers the bottled product after manufacture. Only the second tells you what is in what you bought.

What does ISO 17025 mean on a COA? It is an international accreditation standard for testing laboratory competence, assessed by an external accreditation body. It means the laboratory's methods and quality systems have been independently audited.

Why do some COAs just say "Pass"? Because the issuer chose to report conformance rather than measured values. It is accurate but less informative, since a result just inside the limit and one far below it both read as a pass.

Sources

United States Food and Drug Administration. Current Good Manufacturing Practice in Manufacturing, Packaging, Labeling, or Holding Operations for Dietary Supplements, 21 CFR Part 111.

International Organization for Standardization. ISO/IEC 17025:2017, General requirements for the competence of testing and calibration laboratories.

United States Pharmacopeia. General Chapter <730> Plasma Spectrochemistry.

National Institutes of Health, Office of Dietary Supplements. Dietary Supplements: What You Need to Know.

These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease.