- Being open helps to avoid interactions with medication and problems with an anaesthetic.
- What you tell your doctor is covered by medical confidentiality.
- Before an operation, mention your use in the preliminary consultation or on the anaesthesia questionnaire.
Why it is worth it
THC and CBD can influence how medicines work, for example antidepressants or anticoagulants. The American Heart Association therefore recommends asking about cannabis in everyday medical practice to avoid interactions. German anaesthesia experts advise asking specifically about cannabis and cannabis-based medicines before an operation. You can make it easier by bringing it up yourself.
Medical confidentiality
Doctors and pharmacists commit a criminal offence if they disclose a secret entrusted to them in their professional capacity without authorisation (§ 203 StGB). Company doctors must also observe medical confidentiality (§ 8 Arbeitssicherheitsgesetz). The practice may only pass something on with your consent, where a law allows it or, in exceptional cases, to protect others. An example of such an exception: someone is unfit to drive because of medication or drugs and drives anyway. Even then, the doctor usually has to point this out to you first.
Before an anaesthetic and an operation
In the preliminary consultation or on the anaesthesia questionnaire, say honestly whether you use cannabis, how often and since when. German anaesthesia experts give several reasons for this:
- In people who use cannabis, the anaesthetic often works less well, so they need a higher dose.
- Anyone who uses a lot regularly has a higher risk of complications affecting the heart and lungs and of nausea and vomiting after the anaesthetic.
- After the operation, more painkillers are often needed.
- If you are acutely high before a planned procedure, the appointment may be postponed.
Whether you should take less or nothing at all beforehand is best clarified in the preliminary consultation.
Pregnancy and trying to conceive
Tell your gynaecologist and your midwife too. Why doing without during pregnancy and breastfeeding is recommended is explained in the module Who should avoid cannabis.
Medication plan
Anyone who takes at least three prescribed medicines at the same time is entitled to a medication plan. It also lists medicines you take without a prescription (§ 31a SGB V). Take it with you to every appointment and mention cannabis and CBD products as well.
Checklist to print out
Download the checklist as a PDF (to print out or tick off on screen)
Note down beforehand
- How often do you use, and since when?
- In what form: smoking, vaping, eating?
- With tobacco?
- When did you last use?
- Alcohol, CBD products, other substances?
- All medicines, including those without a prescription, or your medication plan
- What you have noticed: sleep, mood, coughing, palpitations, memory
- Pregnant or trying to conceive?
Questions for the practice
- Does this interact with my medication?
- Is there anything I need to consider before an anaesthetic or an examination?
- Where can I get advice if I want to use less?
Before an operation
- Mention your use in the preliminary consultation or on the anaesthesia questionnaire
- Clarify whether you should take less or nothing beforehand
Sources
- Pharmazeutische Zeitung, cannabis as an interaction partner, 19 January 2022
- American Heart Association, scientific statement on cannabis and cardiovascular health, 5 August 2020 (screening in clinical settings to prevent interactions)
- Anästhesisten im Netz (BDA with DGAI), cannabis use affects anaesthesia, 13 February 2020
- Stein, Fricke, Leffler, does medical cannabis or cannabis use influence perioperative anaesthetic management?, Die Anaesthesiologie 2023 (abstract)
- Kraft, Stromer, the influence of cannabis and cannabinoids on anaesthesia and analgesia in the perioperative phase, Der Schmerz 2020 (abstract)
- § 203 StGB
- § 8 Arbeitssicherheitsgesetz
- German Medical Association and KBV, notes and recommendations on medical confidentiality, data protection and data processing in medical practices, as of 1 October 2025
- § 31a SGB V