How to Read a Certificate of Analysis (COA)
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If you've ever bought THCA product in the UK and noticed a document called a Certificate of Analysis - or COA - attached to the listing, you might have wondered what all those numbers actually mean. This guide breaks it down clearly, so you can read any COA with confidence and know exactly what you're looking at.
What Is a Certificate of Analysis?
A Certificate of Analysis is a third-party lab report that verifies the chemical composition of a cannabis or hemp product. It's produced by an accredited independent laboratory - not the brand selling the product - and confirms what's actually in the product you're buying.
For THCA products in the UK, a COA is one of the most important documents a supplier can provide. It confirms cannabinoid content, checks for contaminants, and verifies the product falls within legal compliance thresholds.
Any reputable THCA supplier should make COAs available for every product they sell. If they don't, that's a red flag.
The Main Sections of a COA
A typical COA is broken into several distinct sections. Here's what each one covers:
|
Section |
What it tests | Why it matters |
| Cannabinoid Profile | Levels of THCA, THC, CBD, CBG, CBN and other cannabinoids |
Confirms potency and legal compliance |
| Terpene Profile | Terpene types and concentrations | Indicates aroma, flavour, and potential entourage effects |
| Residual Solvents | Traces of solvents used in extraction (e.g. butane, ethanol) |
Ensures safe production - high levels are a health risk |
| Heavy Metals | Arsenic, lead, cadmium, mercury | Cannabis absorbs metals from soil - contamination is a serious concern |
| Pesticides | Presence of agricultural pesticides | Confirms the product was grown cleanly |
| Microbials | Bacteria, mould, yeast | Critical for safety - especially in concentrates and hash |
| Mycotoxins | Toxins produced by mould | A secondary check beyond standard microbial testing |
Understanding the Cannabinoid Profile
This is usually the first section people look at, and arguably the most important for THCA products specifically
| Cannabinoid | What It Is |
Typical Range (THCA Flower) |
UK Legal Threshold |
| THCA | The raw, non-psychoactive acid form of THC |
15% – 30%+ | No direct limit - see Delta-9 THC |
| Delta-9 THC | The psychoactive compound. THCA converts to THC when heated (decarboxylation) |
< 0.2% | Must not exceed 0.2% in hemp products |
| CBD | Cannabidiol - non-psychoactive, commonly associated with relaxation |
0% – 5% | No legal limit |
| CBG | Cannabigerol - often called the 'mother cannabinoid' |
0% – 3% | No legal limit |
| CBN | Cannabinol - a minor cannabinoid, mildly sedative |
Trace | No legal limit |
| Total THC | A calculated figure: THC + (THCA x 0.877) |
Varies | Key compliance figure - reviewed case by case |
The key figure to understand is the Delta-9 THC reading. Under UK law, hemp products must not contain more than 0.2% Delta-9 THC. THCA itself is not directly regulated in the same way, but the conversion potential (via heat) is an area of ongoing legal interpretation.
A COA that shows Delta-9 THC below 0.2% is consistent with UK hemp product compliance.
Residual Solvents - What to Look For
This section applies primarily to concentrates like live resin, diamonds, and isolate - products that involve a solvent-based extraction process. After extraction, solvents should be purged from the final product to safe levels
| Solvent | Commonly Used In |
Safe Level (EU/ISO Guidance) |
Red Flag Level |
| Butane (BHO) | Live resin, wax, shatter | < 5,000 ppm | > 5,000 ppm |
| Propane | Mixed hydrocarbon extracts | < 5,000 ppm | > 5,000 ppm |
| Ethanol | Ethanol-extracted oils and hash rosin variants |
< 5,000 ppm | > 5,000 ppm |
| Isopropyl Alcohol | Cleaning solvent, sometimes used in extraction |
< 5,000 ppm | > 5,000 ppm |
| Acetone | Occasionally used in processing | < 5,000 ppm | > 5,000 ppm |
If a concentrate COA shows 'ND' (Not Detected) across residual solvents, that's a strong result. Low ppm figures within safe limits are also acceptable. Anything flagged above safe thresholds should be treated as a concern.
Heavy Metals Testing
Cannabis is a bioaccumulator - it draws nutrients and minerals from soil, which unfortunately includes heavy metals if the growing environment is contaminated. This is why heavy metals testing is non-negotiable for any premium product.
| Metal | Health Risk |
Acceptable Limit (general reference) |
Result to Look For |
| Lead (Pb) | Neurological damage, particularly in children |
< 0.5 ppm (oral) | ND or well below limit |
| Arsenic (As) | Carcinogenic at elevated levels | < 1.5 ppm (oral) | ND or well below limit |
| Cadmium (Cd) | Kidney and bone damage | < 0.5 ppm (oral) | ND or well below limit |
| Mercury (Hg) | Neurological and kidney damage | < 0.3 ppm (oral) | ND or well below limit |
Limits vary slightly depending on the regulatory framework the lab is referencing (EU, USP, ISO). The key thing is that results are below published thresholds - ideally showing ND (Not Detected).
Microbials and Mycotoxins
Microbial contamination - bacteria, mould, and yeast - is a particular concern for flower and hash products that are stored and transported over time. Heat, moisture, and poor packaging all increase risk.
| Contaminant | What It Is | Risk | Pass Result |
| Total Aerobic Count | General bacteria count | High counts indicate poor handling or storage |
< 100,000 CFU/g |
| Total Yeast & Mould | Combined yeast and mould count |
Can cause respiratory issues if inhaled |
< 10,000 CFU/g |
| E. coli | Pathogenic bacteria | Serious health risk | ND / Absent |
| Salmonella | Pathogenic bacteria | Serious health risk | ND / Absent |
| Aspergillus (4 species) | Toxic mould species | Causes aspergillosis - dangerous in immunocompromised individuals |
ND / Absent |
| Aflatoxins | Mycotoxins produced by Aspergillus mould |
Carcinogenic at elevated levels | < 20 ppb total |
| Ochratoxin A | Mycotoxin produced by Aspergillus and Penicillium |
Kidney damage at high exposure | < 10 ppb |
How to Spot a Trustworthy COA
- Not all COAs are created equal. Here's what separates a genuine, reliable lab report from one that should raise questions:
- Issued by an accredited, independent third-party laboratory - not the brand itself
- Includes a date of testing - COAs older than 12 months should be treated with caution
- Contains a batch or lot number that corresponds to the product you're buying
- Covers all key sections - cannabinoids, solvents, heavy metals, and microbials
- Lab is identifiable and searchable - you should be able to find them independently
- Results are clearly marked Pass/Fail or show values against known limits
Summary
| Section | Key Numbers to Check | What a Good Result Looks Like |
| Cannabinoid Profile | Delta-9 THC, THCA % | Delta-9 THC < 0.2% for UK compliance |
| Residual Solvents | Butane, ethanol, propane ppm | ND or below 5,000 ppm per solvent |
| Heavy Metals | Lead, arsenic, cadmium, mercury | ND or below published safety limits |
| Microbials | Total yeast/mould, Aspergillus, E. coli |
ND for pathogens; counts within CFU limits |
| Mycotoxins | Aflatoxins, Ochratoxin A | Below 20 ppb / 10 ppb respectively |
| Terpenes | Individual terpene % | No pass/fail — indicative of quality and profile |
Understanding a COA takes a few minutes once you know what to look for. The brands worth buying from will always make this easy for you.
