How to Read a Cannabis Lab Report: A Consumer's Complete Guide

Every legal cannabis product sold in a licensed dispensary comes with a Certificate of Analysis — a lab report from an independent, accredited testing facility that documents exactly what is in the product. Yet surveys consistently show that fewer than 20% of cannabis consumers have ever looked at one. That is a missed opportunity, because a COA tells you more about a product than any marketing claim ever could.

The first thing to check on any COA is the testing laboratory's accreditation. Look for ISO 17025 certification — this is the international standard for testing laboratory competence. An ISO 17025 accredited lab has been independently audited and verified to produce accurate, reproducible results. Labs without this accreditation may still produce valid results, but you have no independent verification of their methods.

The potency panel is what most consumers look at first. This section lists the cannabinoid content — THC, THCA, CBD, CBDA, CBG, CBN, and others — typically expressed as a percentage of the product's weight. For flower, total THC is calculated as THCA × 0.877 + delta-9 THC, because THCA converts to THC when heated. A product labeled "25% THC" should show this math on the COA. If the numbers don't add up, that's a red flag.

Terpene profiles are increasingly included on COAs and are arguably more useful than THC percentage for predicting effects. A strain with 20% THC and 3% myrcene will feel very different from one with 20% THC and 2% limonene. Myrcene is sedating; limonene is mood-elevating. If you're buying cannabis for a specific purpose — sleep, focus, anxiety relief — the terpene profile is your most reliable guide.

The safety testing panels are where COAs earn their keep. Look for: pesticide screening (should show "pass" or "ND" — not detected — for all regulated pesticides), heavy metals (lead, cadmium, arsenic, mercury should all be below action limits), residual solvents (for concentrates — should be ND or below limits for all solvents used in extraction), microbial contamination (total yeast and mold, E. coli, Salmonella — all should pass), and mycotoxins (aflatoxins and ochratoxin A — should be ND).

Batch numbers matter. A COA is only valid for the specific batch it was tested on. Always verify that the batch number on the COA matches the batch number on the product packaging. Some unscrupulous operators reuse COAs from previous batches — a practice that is both illegal and dangerous. If a product doesn't have a batch number on the packaging, or if the batch number doesn't match the COA, don't buy it.

Date of testing is another critical field. Cannabinoid content degrades over time, particularly when products are exposed to light, heat, or oxygen. A COA from 18 months ago may not accurately reflect the current potency of the product. Most states require COAs to be no more than 12 months old at point of sale; some require 6 months. Check the test date and factor in how long the product has been sitting on the shelf.

QR codes on packaging are increasingly common and make COA verification easy. Scan the code, and you should be taken directly to the lab's website where the COA is hosted — not a PDF on the brand's own website, which could be altered. If the QR code takes you to the brand's site rather than the lab's site, treat that as a yellow flag and verify the lab independently.

The bottom line: a COA is the single most important piece of information about any cannabis product. Brands that make their COAs easy to find and verify are signaling that they have nothing to hide. Brands that bury them, make them hard to access, or use labs without ISO 17025 accreditation are telling you something important about their priorities.