How to Read a Cannabis Lab Test: Understanding COAs Like a Pro

Every legal cannabis product in the United States comes with a Certificate of Analysis — a lab report that tells you exactly what’s in that jar, cartridge, or package. But for most consumers, COAs are an impenetrable wall of numbers, abbreviations, and scientific notation that gets glanced at and ignored.

That’s a mistake. The COA is the single best tool you have for evaluating cannabis quality, safety, and suitability for your needs. Learning to read one takes about five minutes and changes how you shop forever.

What Is a COA?

A Certificate of Analysis is a document produced by a state-licensed testing laboratory that analyzes a cannabis sample for potency, terpene content, and contaminants. Every batch of legal cannabis must pass testing before it can be sold. The COA represents the results of that testing.

Most dispensaries provide COAs through QR codes on packaging, their website, or upon request. If a product doesn’t have an accessible COA, that’s a red flag.

Section 1: Cannabinoid Potency

The potency section is what most consumers look at — and often the only section they understand. It lists the concentrations of major cannabinoids, typically expressed as percentages of dry weight for flower or milligrams per unit for edibles.

Key numbers:

• Total THC: This is the important number. It’s calculated as: delta-9 THC + (THCA × 0.877). Raw cannabis contains mostly THCA, which converts to THC when heated. Total THC tells you the actual psychoactive potential.
• Total CBD: Same calculation — CBD + (CBDA × 0.877).
• Minor cannabinoids: CBG, CBN, CBC, THCV, and others may be listed. These contribute to the entourage effect and can indicate specific therapeutic properties. CBN suggests aged cannabis (not necessarily bad). THCV is associated with appetite suppression and energy.

What to watch for: THC percentages above 35% for flower should be viewed skeptically — while possible, very high-testing results sometimes reflect sampling or testing methodologies that don’t represent the actual product. A 28% THC flower with a great terpene profile will often provide a better experience than a 35% THC flower with minimal terpenes.

Section 2: Terpene Profile

The terpene section is where sophisticated consumers focus. Terpenes are aromatic compounds that influence both the flavor and the effects of cannabis. The science behind terpenes shows they interact with cannabinoids to shape your experience.

Common terpenes and their associations:

• Myrcene: Earthy, musky. Associated with sedation and relaxation. Dominant in many indica-leaning strains.
• Limonene: Citrus. Associated with mood elevation and stress relief.
• Caryophyllene: Peppery, spicy. The only terpene that binds to CB2 receptors. Anti-inflammatory properties.
• Linalool: Floral, lavender. Associated with calming effects and anxiety reduction.
• Pinene: Pine. Associated with alertness and memory retention. May counteract some of THC’s short-term memory effects.
• Terpinolene: Fruity, herbal. Found in many sativa-leaning strains. Less common but distinctive.

Total terpene content matters. Products with total terpene content above 2% generally have more pronounced flavors and effects. Below 1%, the terpene contribution is minimal. Premium flower typically tests between 2-5% total terpenes.

Section 3: Contaminant Testing

This section is arguably the most important and the most overlooked. It tells you whether the product is safe to consume.

Pesticides: Labs test for a panel of pesticides — typically 60-90 specific compounds depending on the state. Results should show “ND” (not detected) or “pass” for all tested pesticides. Any detectable pesticide is a concern, even below action limits.

Heavy metals: Lead, arsenic, cadmium, and mercury testing is standard. Cannabis is a bioaccumulator — it absorbs heavy metals from soil and water. Results should be well below state action limits.

Microbial contaminants: Tests for total aerobic bacteria, yeast and mold, E. coli, Salmonella, and Aspergillus species. This is particularly important for immunocompromised patients. Any detection of pathogenic organisms means the product failed.

Residual solvents: Relevant for concentrates and vape cartridges. Tests ensure that extraction solvents (butane, propane, ethanol, CO2) have been fully purged below safe limits.

Mycotoxins: Toxic compounds produced by certain mold species. Testing is mandatory in most states and particularly important for products stored in humid conditions.

Section 4: Moisture Content and Water Activity

Flower COAs often include moisture content (target: 8-12%) and water activity (target: below 0.65 Aw). These numbers indicate storage quality. High moisture or water activity suggests risk of mold development. Very low moisture means the product is overly dry and may have degraded terpene content.

How to Use COAs When Shopping

Compare terpene profiles, not just THC. Two strains at 25% THC can produce wildly different experiences based on their terpene profiles. Use terpene data to match products to your desired effects.

Check the test date. COAs are batch-specific. A test from six months ago on a product sitting on a shelf means the current cannabinoid and terpene content has likely degraded. Fresh tests (within 60-90 days) are ideal.

Look for full-panel testing. Some COAs only show potency. A complete COA includes potency, terpenes, pesticides, heavy metals, microbials, residual solvents, and mycotoxins. If the contaminant sections are missing, the product may not have been fully tested.

Cross-reference across products. Once you find a terpene profile you enjoy, use COAs to find other products with similar profiles — even across different strains and brands.

The COA transforms cannabis shopping from brand loyalty and budtender recommendations into informed, data-driven decision-making. Five minutes of reading can be the difference between an okay experience and an exceptional one.