How to Test Cannabis
How to Test Cannabis for THC and CBD Potency (2026 guide)
Testing cannabis? Start here
The Cannabis QTest gives you a THC and CBD percentage for the flower in front of you, which is more than the label on most bags will. It measures potency for those two cannabinoids and nothing else, so it can't identify your material or tell you a sample is safe.
The Cannabis QTest measures two things and only two: the percentage of THC and the percentage of CBD in a sample of dried flower or bud. Most cannabis reaches people with no reliable label behind whatever number is on the bag, and potency drifts between crops, within a single harvest, and from one part of a plant to another. Hemp gets sold as strong flower, potent material gets passed off as mild, and the figure printed on a package rarely came from the material in your hand. Running the test gives you a THC and CBD reading for the exact pinch you tested, which is information the seller never handed you.
That reading stops at the edge of two numbers. The test works on flower and bud only, not extracts, oils, vape liquids or edibles, and it reports THC and CBD only, not CBG, CBN, THCV, delta-8 or any other cannabinoid. It cannot see synthetic cannabinoids, pesticides, molds, heavy metals or any other contaminant, and a potency figure never means a sample is safe to consume. Read this page for what the number does and doesn't tell you.
Common cannabis terminology
New to this? These are the words the rest of the page uses. Tap any term to expand it.
THC
Tetrahydrocannabinol, the main psychoactive cannabinoid in cannabis. The QTest estimates its percentage in flower, and that percentage says nothing about contaminants or about how a given sample will affect the person taking it.
CBD
Cannabidiol, a non-intoxicating cannabinoid the QTest reads alongside THC. You get a percentage for CBD in flower, and nothing about the other cannabinoids that may sit beside it in the same material.
Flower / bud
The dried buds of the cannabis plant. Flower is the only form the Cannabis QTest reads; extracts, oils, cartridges and edibles fall outside what the test can measure.
QTest (quantitative test)
A single-use test that quantifies how much of a compound is present rather than identifying what a substance is. The Cannabis QTest quantifies THC and CBD; it does not identify your material or screen it for anything else.
Potency vs identity
Potency is how much of a compound a sample holds; identity is which compound it actually is. The QTest answers a potency question for THC and CBD, and it leaves identity to laboratory analysis.
Synthetic cannabinoid
Lab-made receptor agonists such as the JWH series and MDMB- or ADB-indazole compounds, sprayed onto plant material or dissolved into cartridges. They can be strongly psychoactive while reading low or zero THC on the QTest, so the test cannot rule them out.
Duquenois–Levine spot test
A color spot test sometimes used on cannabis. It doesn't react to synthetic cannabinoids, and it gives false positives with patchouli, spearmint, eucalyptus, nutmeg and tea, so it can't confirm what a sample contains.
Hemp / mislabeling
Hemp is cannabis grown to stay low in THC, and it's routinely sold as stronger flower than it is. A THC percentage from the QTest can flag that gap for the pinch you tested, though it can't tell you why a number came in low.
Cut / adulterant
Anything added to or sprayed onto plant material beyond the cannabis itself. The QTest measures THC and CBD and can't detect an adulterant, so an ordinary-looking reading is no promise that the material is unadulterated.
Which test do I need?
Cannabis QTest. A THC and CBD percentage for the pinch you test, flower and bud only.
Shop the QTest — $24.95Cannabis QTest. A low THC reading flags the mismatch; it won't say why the number is low.
Shop the QTest — $24.95No home test rules a synthetic in or out. Lab analysis is the route that can.
Transparency Testing labOutside what the QTest reads. Send these to the lab for analysis.
Transparency Testing labWhat the Cannabis QTest measures
The Cannabis QTest Kit is a single-use test that estimates the percentage of THC and the percentage of CBD in dried flower or bud. It runs the two measurements separately, each with its own reagent, and you read each result against the evaluation chart printed in the kit. Setup instructions and a walk-through live on the QTest basics page. The number you get describes the cannabinoid content of the material you measured, not whether that material is clean and not what else might be in it.
- Glass vial with colored lid
- Runs the THC determination.
- Plastic dropper bottle with colored cap
- Runs the CBD determination.
- Plastic blister with twist-and-tear-off tip
- Holds the developer solution added to each test.
- Evaluation color chart
- The reference you read your THC and CBD results against.
- Protective gloves (one set)
- Wear them while handling the solutions.
A measuring funnel add-on is $2 and makes it easier to load the specified sample amount without spilling.
Running the Cannabis QTest
- Read the kit instructions first. The sample amount and development time are set for a reason, and guessing at either is the fastest way to a reading you can't trust.
- Use dried flower only. Extracts, oils, cartridges and edibles are outside what the test reads.
- Sample representatively. Take small amounts from several places in your material rather than one spot, since potency varies across a batch and even across a single bud.
- Measure the specified sample amount. The chart is calibrated to that quantity; more or less shifts the result.
- Run the THC and CBD tests separately, each in its own container with its own reagent.
- Add the developer solution and wait the full development time. Reading early gives you a number the reaction hasn't finished producing.
- Compare against the kit's evaluation chart in bright neutral daylight, not under colored or dim light and not against a screen.
How to read the numbers you get
The result belongs to the pinch you measured, not to the whole batch, and repeating the test on material from a different part of the same stash can give you a different figure. The numbers cover THC and CBD only, not other cannabinoids and not terpenes. Two things routinely pull a reading down, and they mean very different things.
- Damp flower reads lower than it is. Water takes up part of the weight you measured, so moisture in the sample crowds out the cannabinoid content the chart is reading. Dry material gives a truer figure.
- A low or zero THC number needs careful interpretation. It can mean weak flower, and it can mean synthetic cannabinoid contamination. Weak flower and synthetic-sprayed flower produce the same low reading here, so the number alone can't separate them.
Synthetic cannabinoids: the gap no home test closes
Synthetic cannabinoid receptor agonists, including the JWH series and MDMB- and ADB-indazole compounds, are sprayed onto plant material or dissolved into cartridges. The QTest can't detect them. Sprayed plant material or a cartridge carrying one reads low or zero THC while staying strongly psychoactive, so a reassuring-looking potency number and a dangerous synthetic can sit in the same sample.
The Duquenois–Levine color spot test can't fill this gap. It doesn't react to synthetic cannabinoids at all, and it gives false positives with patchouli, spearmint, eucalyptus, nutmeg and tea. Neither the QTest nor a spot test can confirm a synthetic is present or rule one out. When flower reads low on material sold as strong, or you have any reason to suspect a spray, lab analysis is the only route that can identify what's there. Send it to Transparency Testing.
What the Cannabis QTest can't do
- It doesn't identify your substance. It quantifies THC and CBD in flower and assumes that's what it's reading; it can't tell you a sample is cannabis in the first place.
- It reads two cannabinoids only. CBG, CBN, THCV, delta-8 and the rest go unmeasured, so the two percentages aren't the whole cannabinoid picture.
- It sees no contaminants. Pesticides, molds, heavy metals and other adulterants don't show up in a potency reading.
- It can't rule out a synthetic. Sprayed material reads low or zero THC while remaining active, so a low number is a question, not a clearance.
- Flower and bud only. Extracts, oils, vape liquids and edibles are outside its range, and there's no reading to trust from them.
- A number is not a safety check. A potency figure for two compounds says nothing about whether the material is safe to consume.
How far you get at home
| What you want to know | How far you can get at home |
|---|---|
| THC and CBD strength of flower | The QTest estimates a percentage for each, for the pinch you measured. Dry the flower first, and sample from several spots |
| Hemp sold as strong flower | A low THC reading flags the mismatch for the sample tested. It can't tell you why the number is low |
| Synthetic cannabinoid spray (JWH, MDMB-, ADB-indazole) | Reads low or zero THC while the material stays active; a spot test doesn't react to synthetics either. Lab analysis is the route that can identify one |
| Other cannabinoids (CBG, CBN, THCV, delta-8) | Not measured. The QTest reports THC and CBD only; lab analysis covers the wider panel |
| Pesticides, molds, heavy metals | Not detectable with a potency test. These require lab analysis |
| Extracts, oils, cartridges, edibles | Outside the QTest's range entirely. Send these to Transparency Testing |
Questions
Can I test extracts, dabs or distillate?
No. The Cannabis QTest reads flower and bud, and concentrated extracts fall outside what it measures. For those, lab analysis is the route that gives you a reliable figure.
Can I test oils, tinctures or vape cartridges?
No, flower and bud only. A cartridge or oil needs lab analysis, which also matters because a cartridge is one of the forms a synthetic can hide in.
Can I test gummies, chocolates or brownies?
No. Edibles are excluded, since the cannabinoid content is distributed through a food matrix the test can't read. For an edible you don't trust, lab analysis is the honest route.
Will this tell me if my flower is sprayed with a synthetic?
No. The QTest measures THC and CBD, and synthetic-sprayed material reads low or zero THC while staying active. Neither the QTest nor a spot test can confirm a synthetic is present. Lab analysis is the only route that identifies one.
My flower read very low THC. Is it just weak weed?
Possibly, but a low reading on material sold as strong is worth investigating rather than shrugging off. Weak flower and synthetic-sprayed flower give an identical low result here, so the number can't separate the two on its own. If it was sold as potent, treat the gap as a reason to send it to the lab.
Does it measure delta-8, CBG, CBN or THCV?
No, THC and CBD only. Those other cannabinoids go unmeasured, so the two percentages aren't a full readout of what's in the flower.
Does it check for pesticides, molds or heavy metals?
No. A potency test sees none of those, and screening for contaminants requires lab analysis.
How accurate is it?
The result depends on how you prepped the sample, how precisely you measured the specified amount, whether you waited the full development time, and the light you read it in. Treat it as a home potency estimate, not a certificate of analysis. Careful, representative sampling in good daylight gives you the closest reading the kit can offer.
Does a good reading mean my cannabis is safe?
No. The figure covers two compounds and nothing more. It says nothing about contaminants, nothing about other cannabinoids, and it isn't guidance on what to take or how much. A number on the chart is information about potency, not permission to consume.
Ready to test?
A THC and CBD potency estimate you can run at home on flower, with orders shipped discreetly.
Single-use · THC and CBD in flower or bud only · Not an identity or safety test
More resources
- QTest purity test kit basics
- Our types of test kits
- Lab testing with Transparency Testing: for the questions a potency test can't answer
- Spectrum color guide
- Safety information
A sample that has been tested should not be considered safe. There is inherent risk when choosing to consume any substance.
Many factors are involved when conducting a test and examining reactions, and The Bunk Police does not assume responsibility for the interpretation of results. Reactions of individual samples can vary depending on lighting differences and the specific mixtures of substances being tested.
Bunk Police kits are intended for identifying unknown substances for harm reduction purposes only. The Bunk Police does not assume responsibility for the use or misuse of this information. Proceed at your own risk.
