Blood draw · 3 analyses
Cannabis (THC)
Measures THC, 11-OH-THC and THC-COOH in your blood; shows whether and how recently cannabis was used.
€ 80,00
All tests
Metals, toxins and medication · Blood
THC (active substance)
THC itself, the substance in cannabis that gives the effect, in your blood; fits use in the past hours to about a day.
At a glance
- Measured in blood
- In 1 test panel
- No special preparation
Explanation
THC (active substance): what is measured?
THC (delta-9-tetrahydrocannabinol) is the substance in cannabis (weed and hash) that gives the effect. After smoking or vaporizing, THC quickly enters the blood and largely disappears from it again within a few hours, because it moves into fatty tissue and is broken down by the liver into 11-OH-THC and THC-COOH. The laboratory measures THC in serum (the fluid part of the blood without blood cells) with gas chromatography-mass spectrometry (GC-MS), a specific method that recognizes the substance by its mass. Because THC stays in the blood only briefly, this value says more about recent use than the breakdown product THC-COOH.
What can it detect?
- Cannabis use in the past hours to about a day
- With daily use or after eating cannabis: use that is sometimes longer than a day ago
Result
What does the result mean?
THC (active substance) too high
A detectable amount of THC fits cannabis use shortly before the sample collection. According to Drugsinfo.nl of the Trimbos Institute, THC is detectable in blood for about 6 to 8 hours after one joint, for 24 hours or sometimes longer with daily use, and also for longer than 24 hours after eating cannabis (for example space cake). So if you smoked in the evening, you can still have THC in your blood the next morning. The level of the value is not a reliable measure of how strongly someone is or was under the influence: with daily use, THC can be detectable without a clear effect. The value says nothing about dependence.
THC (active substance) too low
A value below the laboratory's limit means that at the time of the sample collection there was no detectable amount of THC in your blood. This fits no use in the past hours to about a day. It does not rule out use a few days earlier; then usually only the breakdown product THC-COOH is still detectable.
After an abnormal result
A detectable value does not need medical follow-up on its own. If you have doubts about your own use or want to cut down, you can discuss this with your GP or ask for anonymous advice at Drugsinfo.nl of the Trimbos Institute.
Reliability
How reliable is the test?
GC-MS is a specific and reliable measurement method. The meaning of the value is limited, though: THC shows that cannabis was used shortly before the sample collection, but not exactly when and how much, and not how strongly someone is under the influence. THC says the most together with 11-OH-THC and THC-COOH, which the laboratory measures in the same blood.
What can affect the result?
- THC falls quickly in the first hours after use; the time between last use and the sample collection largely determines the result.
- The laboratory measures in serum; values in serum are higher than in whole blood and cannot be compared one to one with the limits of the police.
- Medicinal cannabis and dronabinol contain THC and rightly give a detectable value; CBD products that contain too much THC can do so as well.
- With daily use, THC is slowly released from fatty tissue and can stay detectable longer than after one-time use.
Who it is for
Who is the test useful for?
Useful for
Useful for a medical question in which recent cannabis use may play a role, especially together with 11-OH-THC and THC-COOH. Not useful as evidence in a procedure, for a medical assessment or to establish whether someone can drive safely: separate tests with their own requirements and limits apply for that. This test is also of no use to find out whether you can safely take part in traffic again after use, because the result only comes later. The result says nothing about whether cannabis use is a problem for you.
How common is it?
In 2025, 7.1 percent of adults in the Netherlands had used cannabis in the past year. Almost 1.5 percent used cannabis (almost) every day.
Trimbos Institute, cannabis figures and trends 2025
Drawbacks and risks
- A detectable value can have unintended consequences if you share it, while it says nothing about fitness to drive at another moment or about dependence.
- A value below the limit can give false reassurance: use from a few days earlier usually can no longer be seen with THC itself.
Get tested
THC (active substance): test panels
THC (active substance) is part of these test panels. You order online and have your blood drawn at a collection point or collect the sample at home.
Evidence
Sources
This explanation is based on Dutch guidelines and independent information. It is general information, not a diagnosis. Discuss an abnormal result with your GP.
More about risks and resultsMore explanations
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