Lab testing
CBD Lab Testing and COAs Explained: How to Read a Certificate of Analysis
A COA is the lab report for one specific batch. Here is how to read the CBD, THC and contaminant results, what ND and LOQ mean, and the red flags to watch for.
A certificate of analysis, or COA, is the report an independent laboratory produces for one specific batch of a product. It shows what is in that batch, how much of it, and whether the result matches the label. For CBD, the lines that matter most are the CBD content, the THC and other controlled cannabinoids, and the contaminant tests. This guide walks through a COA from top to bottom and shows which red flags to look for.
Key takeaways
- A COA belongs to a batch. Match the batch code on your pack to the code on the report.
- Check the CBD result against the label first, then look at THC and the other controlled cannabinoids.
- "ND" means not detected, but it only means something if the lab's detection limit is low enough.
- The 0.2% THC figure often quoted online relates to growing hemp, not to finished products.
- A clean COA describes what is in a product. It is not an authorisation and it is not a health claim.
What a COA is
A COA is a laboratory report for a sample taken from a specific batch. "Third-party" means the lab is independent of the brand, which matters because a seller marking its own homework tells you less than a lab with nothing to gain from the result. Ask which lab produced the report and whether it is accredited. ISO/IEC 17025 is the standard that applies to testing laboratories.
A COA is not a quality mark you can take on trust from a logo. It is a document with numbers on it, and the numbers are what you are checking.
Why the batch matters
CBD products are made in batches, and hemp is an agricultural crop, so the contents can differ from one batch to the next. A single test from two years ago says very little about the bottle in your hand. Every Calm Leaf product carries a batch code on the pack, and the report you want is the one with the same code.
How to read a COA, step by step
- The header. Look for the lab's name and contact details, a report number, the dates of sampling and testing, the product name and the batch code. If any of these are missing, ask why.
- The method. Reports usually name the test methods. Cannabinoids are commonly measured by liquid chromatography and metals by mass spectrometry. You do not need to understand the technique, but a report with no method listed is harder to rely on.
- The cannabinoid profile. This shows how much CBD was found, in mg per ml, mg per gram or as a percentage. Compare it with the label. A 1500mg oil in a 30ml bottle should come out at around 50mg per ml. A small difference is normal; a large gap is a question to put to the seller. (That figure is a worked example, not a real report.)
- THC and other controlled cannabinoids. This is the line most UK shoppers should read twice. The result will be a number, "ND" or "<LOQ". The next section explains what those mean.
- Contaminants. A thorough report can also cover heavy metals such as lead, cadmium, mercury and arsenic, and, depending on the lab and the product, pesticides, residual solvents and microbiology. What is covered varies, so check the report itself. Calm Leaf batch testing covers cannabinoid content, THC, heavy metals and purity. If you want to see a specific test, ask.
- The sign-off. A named person, a date and a clear statement of what was tested.
What ND and LOQ mean
| You see | It means |
|---|---|
| A number, such as 49.2 mg/ml | The amount the lab measured. |
| ND | Not detected. The lab found none above its detection limit. |
| <LOQ | Below the limit of quantification. Something may be present, but too little to measure accurately. |
The detail that matters is the limit behind the result. An "ND" is only as good as the method that produced it. If a lab can only detect THC above a high threshold, a result of ND proves very little. Government Chemist guidance on analytical limits for controlled cannabinoids explains why: the 1mg threshold in UK drug rules is judged against the whole container, not a single dose, so the methods need to be sensitive enough to demonstrate very small amounts.
THC and the UK rules
CBD as an isolated substance in its pure form is not a controlled drug in the UK. THC and some other cannabinoids are. The Home Office position, set out in its drug licensing factsheet, is that a CBD product containing controlled cannabinoids is likely to be controlled, unless it meets the definition of an exempt product. That is why THC testing is not optional for a UK seller, and why the THC line on a COA matters more than any other.
You will often see "0.2% THC" quoted online as the limit for CBD products. It is not. That figure relates to growing approved hemp, not to finished products, which is why we check each finished batch rather than relying on it. Our UK CBD law guide explains the rules in full.
Red flags
- No batch code on the pack, or a report with no batch code.
- No lab name, no date, or no contact details for the lab.
- A report for a different product, or one report reused across a whole range.
- A cropped screenshot instead of the full document.
- THC shown as "ND" with no detection limit or method.
- CBD results that do not match the label and no explanation.
- A report that is much older than the product you are holding.
- A pass or fail stamp with no numbers behind it.
What a COA cannot tell you
A COA describes contents. It does not make a health claim, it is not a guarantee beyond the things the lab tested for, and it is not an authorisation. CBD foods are classed as novel foods in Great Britain, which means they need authorisation before they can be sold legally. As of the FSA's September 2026 board paper, none had been authorised, and the FSA recommended that ministers authorise the first three high-purity applications. You can read the FSA paper for the detail.
In the meantime the FSA runs an interim Public List of products linked to applications going through the process. Appearing on that list is not the same as being authorised, and a clean lab report is a separate thing again. Check both.
Getting the COA for a Calm Leaf product
Every Calm Leaf batch is sent to an independent laboratory and tested for cannabinoid content, THC, heavy metals and purity. To get the certificate that matches your product, follow the steps on our regulatory compliance page, or message the team through the contact page and include the product name and the batch code from your pack.
Free UK delivery on orders over £49, dispatched within 1 working day. Once you have your report, our guides to CBD oil strengths and how much CBD to take in the UK show how to read the label that goes with it.
Frequently asked questions
What does COA stand for?
COA stands for certificate of analysis. It is a report from a laboratory showing the results of tests on a specific batch of a product.
What does ND mean on a CBD lab report?
ND means not detected: the lab found none of that compound above its detection limit. The result is only meaningful if the report also shows how low that limit was.
How can I tell if a COA is genuine?
Check that the batch code matches your pack, that the lab's name, contact details and dates are present, and that the report is complete rather than a cropped image. If you are unsure, ask the seller for the full document and contact the lab to confirm the report number.
Should every batch have its own COA?
Yes. Contents can vary between batches, so a report is only useful for the batch it was run on. The batch code is what links the report to your product.
Is 0.2% THC the legal limit for CBD products?
No. The 0.2% figure relates to growing approved hemp, not to finished products. For finished products the Home Office position is that products containing controlled cannabinoids are likely to be controlled unless they meet the exempt product definition.
Does a clean COA mean a CBD product is authorised by the FSA?
No. A COA describes what is in a batch. CBD foods need novel food authorisation, and the FSA's Public List is an interim record of products linked to applications, not an authorisation.
Sources and further reading
- Home Office: drug licensing factsheet on cannabis, CBD and other cannabinoids
- Government Chemist: guidance on analytical limits for controlled cannabinoids
- Food Standards Agency: CBD Public List
- Food Standards Agency: CBD novel food applications, recommendations to ministers (September 2026)
Related Calm Leaf guides
- CBD Oil Strengths Compared: 500mg vs 1000mg vs 1500mg vs 3000mg
- How Much CBD Should I Take? The UK FSA 10mg Guidance Explained
- How to Choose the Best CBD Oil in the UK: A 2026 Buying Guide
- Is CBD Legal in the UK? THC Limits and the Rules Explained
Last reviewed: 29 October 2026. General information only, not medical advice. Calm Leaf CBD food supplements and cosmetics are not medicines and are not intended to diagnose, treat, cure or prevent any disease. For adults aged 18 and over.
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