Cannabis and the MPU: legal limits, combined use with alcohol and lasting change
What the legal situation in Germany means for cannabis while driving – and why a convincing change involves more than just an inconspicuous measurement value.
In Germany, the medical-psychological assessment is known as the MPU. If you receive a letter from the driving-licence authority after driving under the influence of cannabis, first clarify whether it concerns a traffic offence, doubts about your fitness to drive or an assessment that has already been ordered. These questions have different legal requirements.
This article explains the applicable legal framework and provides guidance for personal reflection. It applies to Germany. The specific regulatory question and the circumstances of the individual case remain crucial.
THC limit and ability to drive
Section 24a(1a) of the German Road Traffic Act (StVG) applies to driving a motor vehicle with at least 3.5 ng/ml of THC in the blood serum. It refers to THC, not the breakdown product THC-COOH. The limit value is not a personal guarantee of safe driving ability. Section 24a of the StVG
Cannabis can impair attention, responsiveness, and the processing of traffic situations. How long this lasts cannot be reliably assessed from subjective feelings alone. Therefore, a generalized waiting period does not provide individual certainty. BIÖG/drugcom: fitness to drive
A person unable to drive safely because of alcohol or other intoxicating substances may commit an offence under section 316 of the German Criminal Code (StGB). Where a specific danger is caused, section 315c may apply. The requirements of each offence must be met. Section 316 of the Criminal Code, Section 315c of the StGB
Cannabis and alcohol – even below 0.5‰ (0.05% BAC)
Section 24a paragraph 2a of the StVG is linked to at least 3.5 ng/ml of THC in the blood serum. In addition, drinking alcohol while driving or starting the drive under the influence of alcohol is prohibited. This rule does not specify an additional threshold of 0.5 per mille.
Example for classification: With 4.0 ng/ml THC and a blood alcohol concentration of 0.2‰ (0.02% BAC), the combined-use offence may apply. Below 3.5 ng/ml THC, these facts alone do not establish that offence; section 24c and criminal provisions may still be relevant. These examples are an interpretation of the statute, not a decision on an individual case. StVG
Medically, the combination is particularly unfavorable: Even small amounts of alcohol can amplify the impairment caused by cannabis. The „first drink, then smoke“ order or vice versa does not create a safe exception. Anyone who has consumed both should organize their journey differently. BIÖG/drugcom: Alcohol and cannabis behind the wheel
A measured blood alcohol level below 0.5 per mille thus does not answer the question of safe driving or all legal questions.
Probation period and under 21 years
Section 24c of the German Road Traffic Act applies during the probation period or before the 21st birthday. It prohibits the consumption of alcohol or THC while driving a motor vehicle, as well as driving under the influence of such substances. The general THC limit is not a clearance here. Section 24c of the StVG
For properly taken, specifically prescribed medical cannabis, there are legal exceptions. However, these do not allow driving when driving ability is lacking. Changes to the treatment should be handled by a physician. Section 24a paragraph 4 and Section 24c paragraph 3 of the StVG, Annex 4 FeV, No. 9.6
When may an MPU be required?
Section 13a of the FeV distinguishes between several cases:
- In cases where there are indications of cannabis addiction, a medical assessment is first required.
- An MPU is required where there are signs or other facts indicating cannabis misuse, repeated traffic offences under the influence of cannabis, a previous withdrawal of the driving licence on those grounds, or a need to establish whether misuse or dependence has ended.
- Exclusive violations of § 24c StVG remain unconsidered in the case of a repeat offense under § 13a Sentence 1 Number 2, letter b.
A first offence does not automatically require an MPU merely because it occurred. However, additional facts may indicate misuse even after a first incident. Combined use also requires consideration of the overall circumstances. Section 13a of the FeV
The penalty decision and the question of longer-term driving fitness must be distinguished. In addition, if there is an additional alcohol problem, the rules of § 13 of the FeV may also apply. Section 13 of the FeV
Misuse, dependence and abstinence
Annex 4 of the German Driving Licence Regulation (FeV) distinguishes cannabis misuse from cannabis dependence. In driving-licence law, misuse particularly concerns inadequate separation between driving and cannabis use that may affect road safety. Misuse or dependence means a lack of fitness to drive.
After misuse has ended, fitness to drive may be restored if the change in cannabis use is stable. Following dependence, Annex 4 requires that dependence no longer exists and that, as a rule, one year of abstinence has been demonstrated. Annex 4 FeV, No. 9.2.1–9.2.4
There is no single required evidence period for all cannabis cases. Before starting a monitoring programme, clarify with a qualified assessment centre which evidence is required and recognised in your procedure. A private consumption diary or an online course attendance certificate does not replace any required forensic evidence of abstinence.
What constitutes a viable change
When reflecting on past behaviour, consider the details: When did you use cannabis? What role did stress, sleep, habits or your social environment play? How did you end up driving afterwards? What has actually changed in everyday life since then?
A sustainable plan identifies concrete alternatives: arrange a safe journey home before using cannabis, hand over your keys, manage cravings, recognise risky situations and seek support. The changes need to fit your own history and be practised repeatedly. Rehearsed answers cannot replace this work.
Anyone who wants to reduce or stop consumption will find it in addiction knowledge article: information on digital self-helpThese resources can provide additional support; they guarantee neither abstinence nor a positive MPU outcome.
In my practice, we can look at consumption patterns, burdens, and everyday changes together. Information on general preparation can be found in Articles on MPU preparation. For a personal inquiry, please use the contact page.
Frequently asked questions
Does „I feel sober“ mean that I can drive?
Our own judgment does not replace a reliable assessment of driving ability or the legal examination. If you are unsure, arrange for another means of transport.
Does every person who consumes cannabis have to prove a year of abstinence?
No. The standard case of one year mentioned in Appendix 4 concerns the restoration of fitness after dependency. An individual clarification is required.
Is an online program also MPU preparation?
The name of a programme does not establish this. Support for changing cannabis use, treatment, MPU preparation and recognised abstinence monitoring serve different purposes.
Sources and timeliness
Status of the source review: October 10, 2026. The basis are the official legal texts linked above and information from the Federal Institute for Public Health. General information; an individual legal review is advisable in the case of a specific decision.
