How to Read a COA: Step-by-Step Breakdown
Start at the top of the COA with the header information. This section identifies the testing laboratory, including its name, address, license number, and ISO 17025 accreditation status. Verify that the lab is accredited and licensed in your state — this is non-negotiable. Next, look at the sample information block. It should list the product name, the producer or brand, the batch or lot number, the date the sample was received, and the date testing was completed. Cross-reference the batch number on the COA with the batch number printed on the product packaging. If they do not match, the COA does not apply to that specific product.
The potency panel is usually the first results section. For flower, potency is reported as a percentage of dry weight. You will see columns for individual cannabinoids: delta-9 THC, THCA, CBD, CBDA, CBN, CBG, and sometimes others. Total THC is calculated using the formula: Total THC = (THCA x 0.877) + delta-9 THC. This accounts for the decarboxylation conversion that occurs when cannabis is heated. Total CBD follows the same logic. For edibles and tinctures, potency is reported in milligrams per serving and milligrams per package. Always check that the listed milligrams match the product label claims.
After potency, review the safety screening panels one by one. The terpene profile shows the concentration of aromatic compounds measured by gas chromatography. Pesticide screening lists dozens of chemical compounds with their detected levels and the state's action limits. Heavy metals testing covers lead, arsenic, mercury, and cadmium with results in parts per million. Microbial testing screens for total yeast and mold, total aerobic bacteria, E. coli, Salmonella, and Aspergillus species. Residual solvents testing is relevant for concentrates and lists compounds like butane, propane, ethanol, and isopropanol. Mycotoxin testing screens for aflatoxins and ochratoxin A. For each panel, check the status column — it should read pass for every category.
Finally, look at the bottom of the COA for the lab director's signature, the date of authorization, and any notes or disclaimers. A complete COA will have all panels filled in with specific numerical values, not just pass/fail. If any panel shows NT (not tested), ask why. Some states allow certain product types to skip specific tests, but a fully transparent brand will test beyond the minimum requirements. Save or screenshot the COA for your records, especially if you find a product you want to repurchase.
Key Takeaways
- •Always verify the lab's accreditation and match the batch number on the COA to the product packaging before trusting the results.
- •Total THC is calculated from THCA and delta-9 THC combined — the raw THCA percentage alone does not reflect the product's actual potency when consumed.
- •Every safety panel should display a pass status; any fail or NT (not tested) result warrants further investigation.
- •A quality COA reports specific numerical values for each analyte, not just pass or fail determinations.
- •Cross-check edible potency in milligrams per serving against the product label to ensure accurate dosing.
Frequently Asked Questions
What does THCA percentage mean on a COA?
THCA (tetrahydrocannabinolic acid) is the raw, non-psychoactive precursor to THC found in unheated cannabis flower. When you smoke or vaporize flower, heat converts THCA into active delta-9 THC through decarboxylation. The total THC formula accounts for this: Total THC = (THCA x 0.877) + delta-9 THC. The 0.877 factor represents the mass lost as CO2 during conversion.
Why do some COAs show different units for the same test?
Different product types use different units. Flower potency is expressed as a percentage of dry weight. Edibles and tinctures use milligrams per serving or per package. Contaminant levels are typically reported in parts per million (ppm) or parts per billion (ppb). Microbial counts use colony-forming units per gram (CFU/g). The units should always be clearly labeled in the column headers.
What if the total THC on the COA does not match the label?
Minor variations of 1-3 percentage points between the COA and the label are common because labels are often printed before final testing, or the label reflects an average across the batch. However, a significant discrepancy — such as a label claiming 30% THC when the COA shows 22% — suggests mislabeling and should be reported to the dispensary and your state's cannabis regulatory agency.
Do I need a science background to understand a COA?
Not at all. The most important things to check are simple: verify the batch number matches your product, confirm all safety panels show pass, and check that the potency numbers are reasonable. You do not need to understand every chemical compound listed. This guide gives you everything needed to evaluate a COA confidently.
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Disclaimer: This guide is for educational purposes only and does not constitute medical or legal advice. Lab testing requirements and regulations vary by state. Always check your local regulations and consult with qualified professionals for specific testing questions. Cannabismarketcap is not a licensed testing laboratory.