How to Read a Cannabis Lab Report

Someone hands you a Certificate of Analysis, three pages of percentages, chemical names and pass or fail columns, and it might as well be a phone bill in a language you don't speak. Here's the version that helps you buy smarter, without needing a chemistry degree.

We covered why this document should exist at all in [Why Lab Tested Cannabis Matters], including the South African study that found 37% of tested market samples failed basic solvent safety limits. This is the walkthrough for what to check once one's in front of you.

The Basics at the Top

Every proper COA should identify the specific sample tested, batch or lot number, the date it was tested, and which lab did the testing. If none of that's on the page, you're not looking at a real report, you're looking at a screenshot of someone else's, or a document with no accountability behind it at all.

Cannabinoid Potency

This is the section most people look at, and for good reason. It lists THC, CBD, and usually a few minor cannabinoids like CBG or CBN, each as a percentage of total weight.

Two numbers worth knowing the difference between. Total THC accounts for the conversion that happens when cannabis is heated, since raw cannabis mostly contains THCA, an inactive precursor that becomes THC when smoked, vaped or cooked. A report showing only THCA without a total THC calculation is telling you less than it looks like it is. Reputable labs show both.

Compare this number against what's on the product label. A meaningful gap between the two is one of the most common ways potency claims turn out to be marketing rather than measurement.

Terpene Profile

Not every COA includes this, but the good ones do. It lists the terpenes present and their concentrations, usually led by whichever one is dominant. This is genuinely useful information, arguably more useful than the indica or sativa label ever was, since it tells you something concrete about how the product is likely to feel. Full breakdown of what these terpenes do in [Cannabis Terpenes: The Real Reason Strains Feel Different].

Contaminant Screening

This is the section that matters most for safety, and the one most often skipped by sellers who only bother testing potency.

Pesticides. Should show a pass against a defined limit for each screened compound, not just a blanket "no pesticides detected" with no specifics.

Heavy metals. Look for lead, arsenic, cadmium and mercury specifically. These accumulate from soil and water and don't announce themselves through smell or taste, which is exactly why a lab number is the only real way to know.

Microbial contamination. Covers mould, yeast and bacteria, including specific pathogens like E. coli and salmonella in more thorough reports. Ties directly into what we covered in [Curing and Storing Cannabis Properly], testing catches this before it reaches you rather than relying on you spotting it yourself.

Residual solvents. Relevant mainly to extracts and concentrates, checking for leftover processing chemicals like butane or ethanol. This is the exact category where the South African market's documented 37% failure rate showed up, arguably the single most important line on the page for anything concentrated.

Mycotoxins. Toxins produced by certain moulds, tested separately from general microbial screening since they can be present even after the mould itself is gone.

Pass, Fail, and Everything in Between

A proper report shows results against a defined limit for each category, not just a vague pass. Look for actual numbers next to actual thresholds. A report that only says "passed" with no visible limit or measurement is asking you to trust it rather than showing you the evidence, which somewhat defeats the point of having one at all.

Red Flags Worth Knowing

No lab name, accreditation number, or contact details anywhere on the document. A test date that's suspiciously old relative to when the product was harvested or packaged. Potency numbers that seem unusually high compared to typical ranges for that product type, without contaminant results anywhere on the same page. And a document that's clearly a stock image or template rather than a specific report tied to a specific batch.

Every LekkerWeed product comes with a COA built exactly the way this article describes, lab name, batch number, potency and full contaminant panel included, so you've got something concrete to check it against.

FAQ

What's the difference between THC and THCA on a lab report? THCA is the inactive form present in raw, unheated cannabis. It converts to active THC when smoked, vaped or cooked. A proper report shows both, along with a calculated total THC that accounts for this conversion.

Does every cannabis product get lab tested? No. In South Africa specifically, testing isn't a legal requirement outside the licensed medical channel, so plenty of product moves through the market with no COA behind it at all. Full context in [Why Lab Tested Cannabis Matters].

What's the most important thing to check on a COA if I only look at one thing? For flower, the contaminant panel, especially heavy metals and microbial results, since those are invisible risks you can't catch any other way. For concentrates and extracts specifically, residual solvents, given how often that category shows up as a failure point in South African testing.

Can a COA be faked? Yes, and it happens. A screenshot with no lab name, no accreditation, or details that don't match the actual product batch are the biggest tells. When in doubt, look up the lab directly rather than trusting the document alone.

Does a terpene profile matter, or is it just for show? It matters. Terpene concentration is a genuinely useful predictor of how a product will feel, more useful than indica, sativa or hybrid labelling, though it's not included on every COA since it's not usually a safety requirement the way contaminant screening is.