Why lab reports matter
A Certificate of Analysis (CoA) is a document produced by a laboratory that details the results of testing performed on a specific product batch. For CBD products, it is the closest thing you have to proof that what is on the label is actually in the bottle.
Given that independent research has found the majority of UK CBD products contain less CBD than advertised — and some contain contaminants that should not be there — the CoA is not optional reading. It is the single most useful tool available to you as a consumer.
Most people never look at them. By the end of this guide, you will know exactly what to check and what each section means.
Step 1: Check who did the testing
The first thing to look at is not the results — it is who produced the report.
Independent third-party testing means the product was sent to an external laboratory with no commercial relationship with the brand. This is what you want. If a brand is testing its own products in its own facility, the potential for bias or conflicts of interest is obvious.
UKAS accreditation is the gold standard for UK laboratories. UKAS (the United Kingdom Accreditation Service) accredits laboratories to ISO/IEC 17025, the international standard for testing and calibration competence. A UKAS-accredited lab has been independently verified to produce reliable, accurate results. Look for the UKAS logo and accreditation number on the report.
If the lab is not named, or the report does not include any accreditation information, treat the results with caution.
Step 2: Check the batch number and date
A CoA should be batch-specific. This means it relates to the exact production batch of the product you are holding in your hand, not a generic test from a previous production run.
Look for a batch number or lot number on the report, and cross-reference it with the batch number on your product's packaging. If they match, the report is relevant to your product. If they do not match, or if the report has no batch number, the results may not reflect what is in your specific bottle.
Also check the date. A CoA from three years ago is less meaningful than one from the current production cycle. CBD products can degrade over time, meaning a test conducted at the point of manufacture may not reflect the product's current composition if it has been sitting on a shelf.
Step 3: Cannabinoid profile
This is the core of the report. The cannabinoid profile section lists the concentrations of individual cannabinoids detected in the product.
CBD content. This is the headline number. Compare it against what the label claims. Industry convention considers a result within 10% of the stated amount to be acceptable. So if a product claims 1000mg of CBD per bottle, a measured result between 900mg and 1100mg is within tolerance. A result of 700mg is not.
The CBD content may be expressed as a total amount (e.g., 1000mg per bottle) or as a concentration (e.g., 3.3% w/v). Make sure you are comparing like with like.
THC content. For a UK-legal product, THC should be below 0.2%. Some reports express this as "not detected" (ND) or "below limit of quantification" (BLoQ). If THC is present above 0.2%, the product may not be legal in the UK.
CBN content. CBN is a controlled substance in the UK. It should ideally be absent or present only in trace quantities. Elevated CBN levels can also indicate that the CBD has degraded, as CBN is a breakdown product of THC.
Other cannabinoids. Full-spectrum products should show a range of minor cannabinoids such as CBG, CBC, and CBDV. If a product is marketed as full-spectrum but the CoA shows only CBD, it may be an isolate-based product with misleading labelling.
Step 4: Contaminant testing
A comprehensive CoA goes beyond cannabinoid content and tests for substances that should not be present.
Heavy metals. The report should test for at least lead, arsenic, mercury, and cadmium. These can be present in hemp if the plants were grown in contaminated soil or if the extraction process introduced contamination. Any detectable levels should be below established safety thresholds.
Residual solvents. If the extraction process uses solvents (ethanol, butane, hexane, etc.), the report should confirm that residual solvent levels in the finished product are below acceptable limits. CO2-extracted products should show minimal or no residual solvents.
Pesticides. Testing for pesticide residues confirms that the hemp was grown without prohibited chemicals, or that any residues present are within safe limits.
Microbiological testing. This checks for bacteria, moulds, and yeasts. It is particularly important for products consumed orally.
Not all CoAs include all of these tests. A cannabinoid-only report is better than no report at all, but a comprehensive report covering contaminants as well provides a much more complete picture of product quality.
Step 5: Know the red flags
Certain features of a CoA — or its absence — should raise concerns.
No CoA available. If a brand does not provide lab reports at all, you have no independent verification of their claims. This is the most significant red flag.
CoA without laboratory identification. A report that does not name the testing laboratory, or that uses a brand's own internal testing, lacks the independence that makes a CoA meaningful.
Non-batch-specific results. A single CoA used for all products across all batches suggests the brand is not testing consistently.
Results that are dramatically different from label claims. If the measured CBD content is more than 20% below the stated amount, the product is significantly mislabelled.
No contaminant testing. A cannabinoid-only CoA is incomplete. The absence of contaminant data does not mean contaminants are absent — it means nobody checked.
Suspiciously perfect results. Laboratory testing always involves some measurement uncertainty. A CoA that shows CBD content at exactly the label claim with no margin should be viewed with scepticism — real-world measurements always have some variance.
Where to find CoAs
Reputable brands typically make CoAs accessible in one of three ways: a dedicated page on their website with reports organised by batch number, a QR code on the product packaging that links to the relevant report, or a batch number lookup tool where you enter your product's lot number to retrieve the corresponding CoA.
If you cannot find a CoA through any of these methods, contact the brand directly and request one. If they are unable or unwilling to provide it, draw your own conclusions.
The honest summary
Reading a CBD lab report is not complicated once you know what to look for. Check who tested it, match the batch number, verify the CBD content against the label, look at THC levels, and check whether contaminants were tested for.
The few minutes this takes could save you from consuming a product that contains less CBD than you paid for, more THC than is legal, or contaminants that have no place in a health product. In a market where independent analysis has shown widespread label inaccuracy, your willingness to check the data is your best protection.