Blood draw
Cannabis (THC)
THC in blood; recent exposure.
€ 80,00
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Metals, toxins and medication · Blood
THC (breakdown product THC-COOH)
The breakdown product of cannabis in your blood (THC-COOH); shows whether you have used cannabis in the past few days.
At a glance
- Measured in blood
- In 1 test panel
- No special preparation
Explanation
THC (breakdown product THC-COOH): what is measured?
This test measures THC carboxylic acid (THC-COOH) in the blood, the breakdown product of THC. THC is the substance in cannabis (hash and weed) that gives the effect; the liver converts THC into THC-COOH, which itself has no effect. Because THC builds up in fatty tissue and is slowly released from it again, THC-COOH stays detectable in the blood much longer than THC itself, especially with regular use. The laboratory also measures THC-COOH in the urine test for cannabis.
What can it detect?
- Cannabis use in the past few days
- With daily or heavy use: use up to several weeks before the sample collection
Result
What does the result mean?
THC (breakdown product THC-COOH) too high
A detectable amount of THC-COOH fits cannabis use in the past few days. According to Drugsinfo.nl of the Trimbos Institute, THC-COOH stays detectable in blood for a number of days up to as long as two months, depending on how much and how often someone used; someone who uses daily will probably always test positive. A higher value usually fits more frequent or heavier use, but the value cannot be converted into the time of use or the amount. A detectable value does not say whether someone is under the influence at that moment, and says nothing about dependence either.
THC (breakdown product THC-COOH) too low
A value below the detection limit means that at the time of the sample collection there was no detectable amount of THC-COOH in your blood. This fits no or little use in the past few days. How long the substance stays detectable differs greatly from person to person; after occasional use, the result can be negative again after just a few days.
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. In a procedure about a driver's license, the assessment always goes through the CBR and an assessing psychiatrist.
Reliability
How reliable is the test?
The measurement is reliable, but its meaning is limited: THC-COOH shows that someone has used cannabis in the past few days, and with daily use also longer ago. Because the breakdown product itself has no effect, the result does not say exactly when it was used, nor whether someone is under the influence or can drive safely. The CBR (the Dutch driver's license authority) also measures THC-COOH in blood when assessing fitness to drive, but with its own cut-off values, through an assessing psychiatrist and a designated laboratory; a result you ordered yourself has no value in that procedure. Medicinal cannabis and some CBD products that contain too much THC can also give a positive result.
What can affect the result?
- The result says nothing about fitness to drive, the time of use or the degree of being under the influence.
- How long THC-COOH stays detectable differs greatly from person to person and depends on how much and how often someone uses and on the amount of fatty tissue.
- Medicinal cannabis and CBD products with too high a THC content can make the result positive.
- Whether someone was under the influence at a certain moment is investigated by the police with a different test (THC itself in saliva or blood); this test is not suitable for that.
Who it is for
Who is the test useful for?
Useful for
Useful if you want to know whether there is still a breakdown product of cannabis in your blood, for example out of your own interest after stopping or cutting down. Not useful as evidence in a procedure, for a medical assessment, to determine the time of use or to establish whether someone can drive safely: separate tests with their own requirements and cut-off values apply for that. The result also says nothing about whether cannabis use is a problem for you; that comes from a conversation, not from blood.
How common is it?
After alcohol and tobacco, cannabis is the most used drug in the Netherlands. In 2025, 7.1 in 100 adults had used cannabis in the past year and almost 1.5 in 100 adults used it (almost) daily. The average THC content of the most popular Dutch-grown weed was 15.6 percent in 2025.
Trimbos Institute, cannabis figures and trends 2025
Drawbacks and risks
- A positive result can have unintended consequences if you share it, while it says nothing about fitness to drive, the time of use or dependence.
- After previous daily use, the result can stay positive for weeks after you have stopped; this can be confusing if you use the result to show that you have stopped.
Get tested
THC (breakdown product THC-COOH): test panels
THC (breakdown product THC-COOH) 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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