How to Read a Cannabis Certificate of Analysis (COA)
A plain walk through a cannabis certificate of analysis: what each part of a lab report shows, which numbers are measured or calculated, and what a single report cannot tell you.
Content last updated . This page has not been medically reviewed.
What a certificate of analysis is
A certificate of analysis (COA) is a lab report for one tested sample of a product. It is meant to show what a laboratory measured in that sample, using a stated method, on a stated date. It is not a promise about every other batch, and it is not a statement about how a product will feel or whether it helps any condition. This page explains how to read the potency part of a COA. Education only: nothing here is dosing, buying or legal advice.The parts to look for
Reports differ from lab to lab, so use this as a checklist rather than a template.| Part of the report | What to look for | Why it matters |
|---|---|---|
| Sample and batch identity | Product name, batch or lot number, sample type (flower, oil, edible) | A report only describes the batch it names. See batch numbers and test dates. |
| Dates | Date the sample was received, tested and reported | Shows how old the result is. |
| Method | The technique, such as liquid or gas chromatography | Changes how acid forms are reported. See testing methods. |
| Cannabinoid table | THC, THCA, CBD, CBDA and others, with units | The acid and neutral forms are separate rows. |
| Total THC / total CBD | A calculated line, not usually a separate measurement | Explained in total THC and total CBD. |
| Limits and "ND" | Limit of detection and quantification, "not detected" marks | See limits of detection and quantification. |
| Uncertainty | A plus-or-minus figure | A result is a measurement with a margin, not an exact fact. |
| Basis | Dry weight, as-received weight, per gram, per unit | Percentages are not comparable across different bases. |
Measured values and calculated values
Most cannabis plants make cannabinoids first in an acid form, such as THCA, and heat converts them to the neutral form, such as THC. A chromatography method that does not heat the sample leaves the acid in place, so the lab reports acid and neutral forms separately and calculates a total. The University of Georgia Cooperative Extension shows the calculation as % Total THC = % THC + (% THCA x 0.877). [1] The same page notes that a gas chromatograph result does not include the acid forms and represents total cannabinoid content. [1] So two reports of the same material can look different on paper depending on method, even when they describe similar chemistry. Read THC vs THCA on a label for the two-number layout.What US hemp rules require labs to report
In the United States, the Agriculture Department's hemp production rule says a laboratory must report the total delta-9 THC concentration on a dry weight basis together with the measurement of uncertainty. [2] It also says measurement of uncertainty must be estimated and reported with test results, and that laboratories must use appropriate, validated methods. [3] This is a rule about hemp production plans (read 2026-10-22, eCFR, 7 CFR Part 990). It is not a rule about every consumer product, and this is not legal advice.What one report cannot tell you
- Whether it is the same product you hold. Only the batch number and test date can link a report to a package.
- Whether the lab is reliable. In a Colorado study of 23 retail flower samples tested by HPLC, the average observed THC was well below label values, and about 70% of samples were more than 15% below the label figure. The authors cited a lack of standardized protocols and financial incentives to market high THC as likely factors. [4] In a later Colorado study of 277 products, observed THC was lower than labeled in both flower and concentrates; 96.0% of concentrates and 56.7% of flower were within 15% of the label. [5]
- Whether a number is inflated by the method. NIST researchers described chromatographic interferences that can inflate the reported delta-9 THC in plant samples. [6] A review of cannabinoid analysis also found that each published method has inherent limitations. [7]
- Whether it works. A potency table says nothing about clinical effects. See why a COA does not prove effectiveness.
Related guides
For hemp and CBD product quality, see certificates of analysis for hemp and CBD products. For contaminant panels, see the guides on pesticides, heavy metals and microbial contamination listed on the Cannabis & Cannabinoids hub.Frequently asked questions
Is a COA the same as a government approval?
No. A COA is a laboratory report on one sample. The US hemp rule sets requirements for how labs report hemp THC and uncertainty, but a COA itself does not mean a regulator approved the product. [2]
Why do two labs give different THC numbers for similar products?
Methods, sample handling and instrument settings differ. A review found each analytical method has inherent limitations, and a NIST study showed that interfering compounds can inflate delta-9 THC in some chromatography methods. [7][6]
Does a high THC number mean a stronger experience?
This page cannot say. A COA is a chemical measurement of a sample, not a measurement of effect. Individual responses vary, and edibles and flower act differently. See the THC guide for the research on effects and risks.
What if the COA has no batch number or date?
Then it cannot be tied to a specific product. Health Canada says its cannabis labels carry the lot number and the date the product was packaged, which is how a label and a lab result are matched. [8]
References
- University of Georgia Cooperative Extension, An Introduction to Hemp Chemistry and Lab Results (Circular 1209). Read 2026-10-22.
- U.S. Agricultural Marketing Service, Electronic Code of Federal Regulations, 7 CFR 990.1 Definitions (hemp production). Read 2026-10-22.
- U.S. Agricultural Marketing Service, Electronic Code of Federal Regulations, 7 CFR 990.3 State and Tribal hemp plan requirements, sampling and testing. Read 2026-10-22.
- Schwabe AL et al. Uncomfortably high: Testing reveals inflated THC potency on retail Cannabis labels. PLoS One 2023. Read 2026-10-22.
- Giordano G et al. Accuracy of labeled THC potency across flower and concentrate cannabis products. Sci Rep 2025. Read 2026-10-22.
- Wilson WB, Yarberry AJ, Goldman S. Chromatographic interferences potentially inflating the levels of delta-9-THC in Cannabis sativa plant samples and possible solutions. J Chromatogr A 2025. Read 2026-10-22.
- Citti C et al. Pitfalls in the analysis of phytocannabinoids in cannabis inflorescence. Anal Bioanal Chem 2020. Read 2026-10-22.
- Health Canada, How to read and understand a cannabis product label. Read 2026-10-22.
Education, not medical advice. This page is for general information. It does not diagnose or treat any condition and is not a substitute for care from a qualified health professional. Natural does not automatically mean safe. Ask a clinician or pharmacist before changing your care, especially if you take medication, are pregnant or breastfeeding, or have a health condition.