How to Test Cannabis
How to Test Cannabis for THC and CBD Potency (2026 guide)
Testing cannabis? Start here
The Cannabis QTest measures THC and CBD in flower or bud. If you're worried a sample is sprayed with a synthetic cannabinoid, that's a different question — and no home test answers it.
Cannabis potency varies widely between strains, growers and batches, and unregulated flower comes with no reliable label. Testing gives you information you wouldn't otherwise have — a THC and CBD figure for the material in front of you. It cannot make a sample safe, and it cannot tell you what's in a sample beyond those two cannabinoids.
What the Cannabis QTest tells you, and what it doesn't
The Cannabis QTest Kit ($24.95, single use) determines the percentage of THC and CBD in cannabis flower or buds. That's the whole supported scope — one sample type, two analytes.
| Question | Does the QTest answer it? | Detail |
|---|---|---|
| How much THC and CBD is in this flower or bud? | Yes — this is what it's for | Two separate measurements, each read against the evaluation chart supplied in the kit |
| Will it work on concentrated extracts — shatter, wax, rosin, distillate? | No | The kit does not work with concentrated extracts. Earlier versions of this page listed extracts as both supported and unsupported; the product page is the correct one — extracts are out of scope |
| Will it work on oils, tinctures or vape liquid? | No | We previously claimed support for liquids, oils and vape liquid. That claim wasn't supported by the kit and has been withdrawn |
| Will it work on gummies, chocolates, brownies or other edibles? | No | Explicitly excluded. Sugar, fat and cocoa are not in scope, and a number from one shouldn't be trusted either way |
| Will it detect a synthetic cannabinoid? | No | It measures THC and CBD. A synthetic such as JWH-018 or one of the current MDMB- or ADB- compounds is neither, so it is simply not seen — see the next section |
| Does it measure other cannabinoids — CBG, CBN, THCV, delta-8? | No | Two analytes only. Anything else present is invisible to the test |
| Does it detect pesticides, moulds, heavy metals or growth regulators? | No | None of these. Contamination is a laboratory question |
| Does it identify the strain? | No | No chemical test identifies a strain or cultivar |
| Does it tell you the sample is safe? | No | It's a potency measurement for two compounds in one pinch of flower. That's all |
- Glass vial with colored lid, containing dry crystals
- For determining THC concentration.
- Plastic dropper bottle with colored cap
- For determining CBD concentration.
- Plastic blister with twist-and-tear-off tip
- Developer solution.
- Evaluation color chart
- Read your result against this, in bright neutral daylight. Don't substitute a chart from a photo or another kit.
- Protective gloves
- One set. Wear them — the solutions are chemical reagents.
Single use, $24.95. Read the instructions and safety information in the box before you open anything; there's no second attempt in the package. A plastic measuring funnel is available as a $2 add-on.
- Read the instructions and safety sheet first, then put the gloves on.
- Use flower or bud only — dry, and broken up evenly. Not extract, not oil, not an edible.
- Sample representatively. Cannabinoid content differs between the top of a cola and the lower leaf material, and between buds from the same plant. Take a little from several places and mix it, rather than testing one crumb.
- Measure out the sample amount the instructions specify — the funnel add-on makes this less messy. The measurement is only as good as this step.
- Run the THC vial and the CBD dropper bottle as separate procedures, in the order the instructions give.
- Add the developer solution using the twist-and-tear tip. Let each reaction develop for the full stated time before reading.
- Compare against the kit's evaluation chart in bright neutral daylight. Photograph the vial and the chart together.
- They describe the pinch you tested. Not the bag, not the plant. Sample properly or accept that the figure is local.
- They're THC and CBD only. Other cannabinoids and terpenes aren't in the result, so the two numbers won't sum to anything meaningful about the whole sample.
- Moisture shifts the result. Damp flower reads lower because water is taking up part of your measured sample weight.
- A number is not a dose. Tolerance, route, and how much you actually inhale or eat aren't in the measurement.
- A low or zero THC reading has more than one explanation, and one of them is dangerous. See the next section before you act on it.
Synthetic cannabinoids — the gap no home test closes
Synthetic cannabinoid receptor agonists — the JWH series, and the MDMB- and ADB- indazole compounds that dominate now — are sprayed onto inert or low-potency plant material, or dissolved into cartridges sold as THC vapes. They aren't THC. They're often far more potent by weight, with a much narrower margin between an effect and a medical emergency, and they've been linked to seizures, psychosis and deaths in ways cannabis has not.
There are two things to understand about testing them, and both are limitations rather than solutions.
The kit measures THC and CBD. A synthetic cannabinoid is neither, so sprayed plant material or a "THC" cartridge containing one reads low or zero THC. The material can be strongly psychoactive and still produce a near-zero number.
So a low reading on something that was sold to you as potent, or something that felt strong when other people used it, is a red flag rather than a disappointment. Do not respond by using more of it. Get it lab tested and log it in BunkLeaks.
We don't sell a cannabis color reagent, and this is why. The classic cannabis spot test is Duquenois–Levine, and it has two problems that make it useless for the question people actually want answered.
- It doesn't react to synthetic cannabinoids. Compounds including JWH-018 and JWH-019 give no Duquenois–Levine reaction, so sprayed material can test negative for cannabis while being more dangerous than cannabis.
- It isn't specific to cannabis anyway. Documented false positives include patchouli, spearmint, eucalyptus, nutmeg and ordinary tea. A positive doesn't establish cannabis and a negative doesn't establish its absence.
Put together: spot testing cannot tell you whether a sample is sprayed. Nothing you can do at a kitchen table can. If that's your question, the answer is instrumental analysis.
| What's actually in it | Cannabis QTest | Duquenois–Levine spot test | What it takes to confirm |
|---|---|---|---|
| Cannabis flower or bud | Works as designed — a THC and a CBD percentage | Reacts, but so do several kitchen herbs. Adds nothing to the QTest | The QTest is the right tool for potency |
| Plant material sprayed with a synthetic cannabinoid | Low or zero THC. Do not read that as "weak" | No reaction to JWH-018, JWH-019 and similar compounds — a negative here means nothing | Lab analysis |
| A "THC" cartridge containing a synthetic | Out of scope — the kit doesn't support vape liquid at all | Not applicable | Lab analysis |
| Hemp or CBD-dominant flower sold as high-THC | Catches this — low THC alongside a substantial CBD figure | Reacts to both. Can't tell them apart | The QTest is sufficient to spot the mismatch |
| Concentrated extract, oil or distillate | Out of scope. Any number you get is unreliable | Non-specific, and no potency information | Lab analysis |
| Edibles — gummies, chocolates, brownies | Out of scope | Non-specific and confounded by the food matrix | Lab analysis |
| Pesticides, growth regulators, mould, heavy metals | Not measured | Not measured | Lab analysis |
| Non-cannabis plant matter as filler | Shows up indirectly as a lower THC figure | Can false-positive on the filler itself | Lab analysis, or visual and microscope inspection |
Which test do I need?
THC and CBD percentages for cannabis flower or bud. Single use.
Cannabis QTest — $24.95The QTest catches this — a low THC figure next to a substantial CBD figure.
Cannabis QTest — $24.95No home method answers this. A low THC reading is a warning sign, not a measurement of the synthetic.
Lab testing serviceOutside the kit's scope entirely. Don't run it and don't trust a number from it.
Lab testing serviceStep by step
- Check your sample type. Flower or bud only. Extracts, oils, cartridges and edibles are out of scope — stop here for those.
- Dry it and break it up evenly. Damp material reads low.
- Sample from several places and mix, so the figure represents the batch rather than one crumb.
- Measure the sample amount the instructions specify. Use the funnel if you bought one; guess the quantity and you've guessed the answer.
- Run the THC test and the CBD test as separate procedures, in the order given, adding the developer solution with the twist-and-tear tip.
- Let each reaction run its full time, then read against the kit's evaluation chart in bright neutral daylight.
- Interpret a low THC figure carefully. Weak flower and synthetic-sprayed material look identical on this test.
- Report it. Log the result in BunkLeaks, especially if what you found doesn't match what you were told.
- Running it on an extract, oil, cartridge or edible. The kit isn't calibrated for any of them.
- Damp or unevenly dried flower.
- Eyeballing the sample quantity instead of measuring it.
- Testing one crumb and treating the number as a batch figure.
- Reading before the reaction has finished developing.
- Dim, warm or colored lighting. The result is read by eye against a printed chart.
- Using a chart from a photo, a different kit, or a screen instead of the one in the box.
- Treating a low THC reading as proof the sample is weak rather than as a question that needs answering.
Your result wasn't what you expected
- Report it. Log the sample, the source and both numbers in BunkLeaks. Sprayed material circulating in your area is a warning for everyone buying from the same place.
- Find out what's actually in it. A near-zero THC reading on material that was sold as potent, or that produced strong effects for someone else, is exactly the case for instrumental analysis. Our lab testing service can identify synthetic cannabinoids that the QTest cannot see.
- Do not smoke more to compensate. If the active compound is something the test can't measure, increasing the amount is the worst available response.
- Treat seizures, blackouts or severe agitation as an emergency. Those are far more characteristic of synthetic cannabinoids than of cannabis. Call emergency services.
- Rule out the test itself first. Re-run with properly dried material, a correctly measured sample and daylight before drawing conclusions.
- Don't use alone.
Questions
Can I test extracts, dabs or distillate?
No. The Cannabis QTest does not work with concentrated extracts. An older version of this page listed extracts as supported in one sentence and unsupported in the next — the product page is correct, and extracts are out of scope.
Can I test oils, tinctures or vape cartridges?
No. This page previously claimed support for liquids, oils and vape liquid. That claim wasn't supported by the kit and we've withdrawn it. The kit covers flower and bud.
Can I test gummies, chocolates or brownies?
No — edibles are explicitly excluded. For an edible whose label you don't trust, lab analysis is the honest answer.
Will this tell me if my weed is sprayed with a synthetic?
No. The QTest measures THC and CBD, and a synthetic cannabinoid is neither — so sprayed material reads low or zero THC while still being strongly, and unpredictably, active. Color spot testing doesn't help either: Duquenois–Levine gives no reaction to JWH-018 or JWH-019, and false-positives on things like patchouli, nutmeg and tea. This needs a laboratory.
My flower read very low THC. Is it just bad weed?
Possibly. But if it was sold as strong, or it felt strong, a near-zero THC number is a reason to stop rather than a reason to shrug. Weak flower and synthetic-sprayed flower produce the same reading on this test.
Does it measure delta-8, CBG, CBN or THCV?
No. Two analytes only: THC and CBD. Anything else present is invisible to the test.
Does it check for pesticides, moulds or heavy metals?
No. Those are contamination questions and they need a laboratory.
How accurate is it?
Accuracy depends on how well you dried and mixed the material, how carefully you measured the sample, whether you allowed the full development time, and the light you read the chart in. It's a home potency estimate, not a certificate of analysis.
Does a good reading mean my cannabis is safe?
No. It's a potency figure for two compounds in one pinch of flower. It says nothing about contaminants, nothing about other cannabinoids, and nothing about whether the amount you plan to use is right for you.
Ready to test?
Serious drug checking at home. Orders ship within 24 hours.
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More resources
- QTest purity kit basics — full instructions for every QTest
- Our types of test kits
- Lab testing service — the only way to identify a synthetic cannabinoid
- BunkLeaks — report a mislabelled or sprayed sample
- 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.
