How to read a cannabis COA (certificate of analysis) — and why it matters

A certificate of analysis, or COA, is a lab report that tells you exactly what’s in a cannabis product before you consume it. It covers cannabinoid potency, terpene content, and — critically — whether the product has been tested for pesticides, heavy metals, and microbial contamination. If a cannabis brand can’t show you a COA for every batch, that’s a reason to look elsewhere. Here’s how to read one.

What is a COA and who issues them?

A COA is issued by an independent, accredited third-party laboratory that has no financial relationship with the cannabis producer. That independence is what makes it trustworthy. The lab tests a sample from the batch, measures its chemical composition, and produces a report that the brand is then required to make available to consumers.

Reputable cannabis retailers publish COAs for every batch — not just for product lines. Batch-specific testing matters because the same strain can test differently from harvest to harvest depending on growing conditions, curing time, and plant health.

How to read cannabinoid potency numbers

The cannabinoid section of a COA lists the concentration of compounds like THC, CBD, CBG, and CBN, usually expressed as a percentage of the total weight. THC (tetrahydrocannabinol) is the primary psychoactive compound. CBD (cannabidiol) is non-intoxicating and associated with relaxation and anti-inflammatory effects.

You’ll often see two THC numbers: THC and THCA. THCA is the raw, unactivated form that converts to THC when heated (smoked or vaped). To estimate the actual THC potency of a product you’ll smoke, use this formula: Total THC = THC + (THCA × 0.877). Most reputable labs calculate this for you.

What terpene testing tells you

The terpene panel lists aromatic compounds by percentage. These directly shape your experience — myrcene promotes relaxation and sedation, limonene elevates mood, caryophyllene provides anti-inflammatory effects, and pinene sharpens focus. A strain with a rich terpene profile (2%+) will typically deliver a more nuanced, full-spectrum experience than a stripped-down concentrate.

If you’re choosing between two products with similar THC percentages, the terpene panel is often the more useful differentiator.

Pesticide, heavy metal, and microbial testing

The safety section of a COA confirms whether the product tested negative for pesticide residues, heavy metals like lead and arsenic, and microbial contaminants like mould, E. coli, and salmonella. These should all show “pass” or “ND” (not detected). Any “fail” result means the batch should not be sold — full stop.

This section of the COA is the most important from a health perspective, and it’s the one most consumers skip. Don’t. Cannabis that hasn’t been tested for contamination is a genuine risk, especially for immunocompromised individuals.

Full transparency — every batch, every time

Every West Coast Treez product comes with a batch-specific COA from an accredited independent lab. You can view the full results before you buy — cannabinoid content, terpene profile, and all safety panels. View all West Coast Treez lab results →