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A certificate of analysis (COA) is a lab report for one specific lot of an ingredient or finished product. To read it, match the lot number to your product, then compare every result against its specification. Check that each test names a method, that nothing is missing, and that a quality person signed and dated the report.
Founders often receive their first COA with the first production run and file it without reading it. That’s a mistake. The certificate of analysis is your proof that the product in the box matches the label. Retailers, Amazon and regulators may ask for it, and it’s the first thing to check if a customer complains. This guide walks through each part of a COA and the 7 checks we recommend on every one.
What a certificate of analysis is for
There are two kinds of COA in a typical supplement or skincare project:
- Raw material COAs. Each ingredient supplier sends one with every lot. It shows that the ingredient meets its specification before it goes into your batch.
- Finished product COAs. The manufacturer issues one for your finished batch. It shows that the product you’re about to sell meets the specification you agreed on.
At Welsdom, we review the supplier’s certificate of analysis for incoming raw materials, and we provide a COA with each finished batch. Both documents matter. A finished product is only as good as the ingredients that went into it.
The parts of a certificate of analysis
Most COAs follow the same layout, even when the design differs. Here is what each section tells you.
| Section | What it shows | What to check |
|---|---|---|
| Header | Product name, lot or batch number, manufacture date, expiry or retest date | The lot number matches the label on your stock |
| Test parameter | What was tested, such as identity, potency, microbial counts or heavy metals | Every test in your specification appears |
| Specification | The acceptable limit or range for each test | It matches the specification you approved |
| Result | The actual value the lab measured | It falls inside the specification |
| Method | The test method, such as HPLC or a pharmacopoeia method | A method appears for each test |
| Sign-off | Name, signature and date from quality staff | Someone accountable approved the release |
7 key checks on every certificate of analysis
1. Match the lot number
First, confirm the lot or batch number on the certificate of analysis matches the number printed on your bottles or pouches. A COA for a different lot tells you nothing about the stock in your warehouse.
2. Compare each result with its specification
Next, read across each row. The result should sit inside the limit or range. Also watch for results that sit right at the edge. A pass is a pass, but it may be worth a conversation if potency keeps landing near the minimum.
3. Check the units
Units trip people up. Potency may appear in mg per capsule, mg per serving or as a percentage. Microbial counts often use CFU per gram. Make sure the units on the COA match the units in your specification and on your label.
4. Look for missing tests
A short COA isn’t always a good sign. Compare the list of tests with your agreed specification. For a supplement, the finished product specification usually covers identity, quantity or potency of each active, purity and microbial quality. If a test you expected is missing, ask why.
5. Read the “conforms” lines carefully
Some COAs show “conforms” or “pass” instead of a number. That’s normal for tests such as appearance or odour. However, for potency or contaminants you want a measured value, so you can see how close it sits to the limit.
6. Check the method and the lab
Each test should name a method. Also note whether the manufacturer’s own lab or an outside lab ran it. Both can be valid, but you should know which one you’re reading.
7. Confirm the sign-off and dates
Finally, a quality person should sign and date the report. The test date should come after the manufacture date and before release. An unsigned certificate of analysis is a draft, not a release document.
What the rules say about COAs
Canada. Health Canada’s GMP guide for natural health products says a finished product specification must cover purity, plus the identity and quantity per dosage unit of each medicinal ingredient. If the label shows potency, the specification must cover that too, along with the test methods. A quality assurance person must approve the specification and every change to it. The guide also lists a certificate of analysis for each lot, showing that it meets its specification, as one example of GMP evidence.
The same guide expects importers to review the supplier’s certificate of analysis with each lot they receive. As an example of a confirmatory program, it suggests testing at least 1 lot per dosage form per supplier per year.
United States. FDA’s dietary supplement GMP rule, 21 CFR Part 111, requires at least one test or examination to verify the identity of every dietary ingredient. For other components, a manufacturer may rely on a supplier’s certificate of analysis only after it qualifies that supplier. The COA must show the test methods, limits and actual results, and the manufacturer must re-confirm it from time to time.
In short, a certificate of analysis is a trust document. Good manufacturers check their suppliers’ COAs rather than simply filing them.
Red flags on a certificate of analysis
Watch for these warning signs:
- The lot number doesn’t match your product.
- Results appear without specifications, so you can’t tell what “good” looks like.
- Tests from your agreed specification are missing.
- Every result is “conforms,” including potency.
- There’s no signature, no date, or the dates are out of order.
- The product name or format differs from what you ordered.
If you see any of these, ask your manufacturer before you release the stock to customers. Most issues turn out to be paperwork errors. Still, you want them fixed before a retailer asks.
How COAs connect to stability and shelf life
A release COA tells you the product met its specification on the day of testing. It doesn’t tell you how the product holds up over time. That’s the job of stability testing, which re-tests samples over months. Our guide to stability testing for skincare and supplements explains how studies confirm the expiry date. Also, our post on testing required for supplement products in Canada covers each test type in more detail.
Frequently Asked Questions
What is a certificate of analysis?
A certificate of analysis is a lab report for one lot of an ingredient or finished product. It lists each test, the acceptable limit, the actual result and the method, plus a quality sign-off.
Who issues the COA for my finished product?
Your manufacturer issues it for each finished batch. At Welsdom, a COA comes with each batch, and we review supplier COAs for incoming raw materials.
What tests should a supplement COA include?
It should cover every test in your agreed specification. That usually means identity, potency or quantity of each active, purity and microbial quality, plus contaminants such as heavy metals where they apply.
Is a supplier’s COA enough on its own?
Not always. In the US, FDA requires an identity test for every dietary ingredient and lets manufacturers rely on supplier COAs for other components only after they qualify the supplier. Health Canada also expects review of supplier COAs.
How long should I keep COAs?
Keep each COA with your lot records for at least as long as the product is on the market, and longer if your retailer asks. Your manufacturer keeps its own batch records too.
When you’re ready to build a formula with clear specifications and a COA for every batch, start on our custom formulation page.