Cannabis and driver’s license: Explained: THC limit of 3.5 ng/ml
With the Cannabis Consumption Act (KCanG), Germany has not only liberalized cannabis consumption but also redefined traffic regulations. The previous blood limit of 1.0 ng/ml THC has been abolished — in its place is a new limit of 3.5 ng/ml THC in the blood serum. Sounds simple, but it is not: anyone who drives after consuming cannabis navigates between criminal law, traffic offenses, and driver’s license regulations — and these three systems apply differently.
The new THC limit: 3.5 ng/ml in the blood serum
Since October 2024, a legal limit of 3.5 ng/ml THC in the blood serum applies to drivers (§ 24a StVG new version). Anyone who is at or below this level while driving does not automatically commit a traffic offense — provided there are no specific signs of impairment.
Important: The limit applies to THC, not to THC-COOH (the inactive metabolite). THC-COOH can still be detected in the blood for days after consumption, but it is not relevant for the new limit. Only the active ingredient THC is decisive.
For those under 21 years old and novice drivers in their probationary period, the absolute rule of sobriety while driving still applies — the 3.5 ng/ml limit does not apply here.
What happens in case of exceeding the limit
Anyone who exceeds 3.5 ng/ml risks:
- Administrative offense: 500 € fine, 1 point in Flensburg, 1 month driving ban — on first offense
- Repeat offense: On second offense within 12 months, the fine doubles to 1,000 €, 2 points, 3 months driving ban
- Combined use (Cannabis + Alcohol): Anyone who consumes both cannabis and alcohol and drives is already punishable from the first offense — regardless of the THC level
- Driving fitness assessment (MPU): In case of suspicious findings or repeat offenders, the licensing authority may order a medical-psychological examination
Criminal law becomes relevant if a concrete danger arises due to THC influence (§ 315c StGB) or an accident occurs. Then, a fine or imprisonment may be imposed, regardless of the limit.
How long after consumption can you drive?
This is the practically decisive question — and it cannot be answered in a general way. The breakdown of THC in the blood is highly individual and depends on consumption frequency, body fat, form of consumption, and quantity.
Reference values for occasional users:
- 1–2 hours after smoking/vaporizing: THC blood concentration is usually still significantly above 3.5 ng/ml
- 4–6 hours after consumption: Often below the limit value for occasional users — but no guarantee
- Regular users: THC accumulates in fat tissue and can still be above 3.5 ng/ml 12–24 hours after the last consumption
The only safe recommendation from traffic medicine: At least 8 hours waiting time after consumption, better more — and with regular consumption, significantly longer. Home tests (saliva tests from the pharmacy) measure THC in saliva, not in blood, and are unsuitable for estimating blood serum limit values.
Medical cannabis patients driving
For patients who consume cannabis by prescription, the same legal regulations apply — the 3.5 ng/ml limit does not make an exception for medical use. This is a central issue: with regular use, the THC blood level can remain above the limit for a prolonged period.
Doctors and pharmacists are obliged to inform patients about driving suitability. Anyone who takes cannabis daily as medication and must drive a car should discuss with their treating physician:
- Whether a dosage adjustment is possible (e.g., taking it only in the evening)
- Whether a blood test relevant to driving suitability can provide clarity
- Whether the drug enforcement authority is already aware of the consumption in the specific case (relevant for driver’s license status)
The driver’s license office can request a medical opinion on driving suitability in cases of known THC consumption — even for patients.
Police Check: Procedure and Rights
During a traffic stop with suspicion of cannabis use:
- The police first use a drug rapid test (saliva) — a positive result leads to a blood test
- Blood draw is performed by a doctor — the result determines legal consequences
- No obligation to speak: Those asked about consumption do not have to say anything
- You must present your driver’s license — this is mandatory
A positive saliva test alone is not sufficient for a conviction — the blood sample decides.
Those who want to know how long THC is generally detectable:
Those who drive while combining cannabis and alcohol risk more than two individual offenses:
Alongside road traffic, there are specific regulations for athletes:
The THC limit while driving in detail — what 3.5 ng/mL means and when you are allowed to drive: Cannabis and Driving: THC Limit and Driver’s License Risk — §24a StVG, roadside tests, MPU and practical time recommendations.
Frequently Asked Questions about Cannabis and Driver’s License
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