A certificate of analysis, or COA, is a laboratory report showing what is actually in a specific batch of a product — including any heavy metals, which occur naturally in the soil and water that plants and minerals come from, and in trace amounts in many everyday foods too. A COA lets you see whether the level found in that batch falls within recognised safety limits, rather than taking a seller's word for it.
Heavy metals get mentioned a lot in supplement discussions, often in a way that makes them sound like proof of contamination. The reality is more mundane: certain metals such as lead, arsenic, cadmium and mercury are present at low levels almost everywhere in the environment, and any plant grown in soil, or any mineral dug from rock, will pick up trace amounts. The question is not whether they are detectable, but whether the amount is within the limits set for food supplements.
Why do heavy metals turn up in supplements at all?
Plants take up whatever is in the soil they grow in, including naturally occurring metals, and pass small amounts through to their roots, leaves and seeds. Minerals dug from the ground, including materials like shilajit, come from rock that has its own natural mineral content. Neither of these facts means a product is unsafe. It means testing exists to check that levels stay within accepted limits, the same way it does for many foods you already eat.
What does matter is scale and sourcing. Some regions and some plant species accumulate more of certain metals than others, which is exactly why batch testing rather than a one-off product approval is the meaningful safeguard.
What is a certificate of analysis?
A COA is a document produced by a laboratory after testing a sample from a specific batch of product. It typically states what was tested for, the method used, the result for each substance, and the limit that result is being measured against. A trustworthy COA is tied to a batch number that matches the pack in your hand, not a generic document reused across every batch a supplier has ever made.
Reputable sellers test for the substances most relevant to their product type — commonly heavy metals, and for some products microbial contamination as well — and use an accredited, independent laboratory rather than in-house testing alone.
What is a batch number, and why does it matter?
A batch, or lot, number identifies a specific production run of a product. Because raw materials vary slightly from batch to batch, testing one batch does not guarantee the results of the next. A batch number lets a certificate of analysis be tied to the exact product you are holding, and lets a seller trace a problem back to its source if one is ever found.
If a product carries a batch number but the seller cannot produce a COA matching that number, the batch number alone is not telling you much.
What should a COA actually show you?
- The batch or lot number, matching the pack
- The date the sample was tested
- The name of the testing laboratory
- Each substance tested for, its result, and the limit it is compared against
- A clear pass or fail against that limit
You do not need a science background to check these points. If any of them are missing, or the document reads more like a marketing sheet than a lab report, treat that as a gap rather than a formality.
What should you do if a seller will not provide one?
Ask directly, and ask for the version matching the batch number on your pack. A seller who tests routinely will have this ready. If a seller is vague, delays repeatedly, or provides a document with no batch number, testing date or laboratory name, that is a reasonable reason to buy elsewhere. Testing costs money, and a business that has paid for it usually wants you to see the result.
This is one of the more useful questions to ask when you are comparing sellers generally — our guide on how to spot quality shilajit covers several others.
Independent lab report vs marketing claim
| Independent laboratory report | Marketing claim alone | |
|---|---|---|
| Issued by | Accredited third-party lab | The seller, or no one |
| Tied to a batch | Yes, by batch number | Rarely specified |
| States a method and limit | Yes | No |
| Can be checked by you | Yes, on request | No independent verification |
Common questions
Does the presence of any heavy metal mean a product is unsafe?
No. It means the result needs to be read against the relevant limit. Trace levels within that limit are expected and are not the same thing as contamination.
Should every supplement come with a COA?
It is good practice, particularly for mineral- and plant-derived products where natural variation is higher. Not every category carries the same risk profile, so expectations differ somewhat by product type.
Can I trust a COA that a seller has written themselves?
Look for one issued by an independent, accredited laboratory rather than produced in-house. Independence is what gives the document its value.
How often should batches be tested?
Ideally every batch, since raw material composition can shift between production runs. A single historic test covering an entire product range is a weaker guarantee.
Where can I see an example of this done properly?
Our own laboratory analysis results show what we test for and why, and our guide to what shilajit actually is gives useful background if you are new to the category. You can browse tested products in our shilajit collection.
Food supplements should not be used as a substitute for a varied and balanced diet or a healthy lifestyle. If you are pregnant, breastfeeding, taking medication or under medical supervision, speak to your doctor or pharmacist before starting any supplement. We are not able to give medical advice.