Medical Cannabis and Driving: What Patients Must Know
What Researchers Found About and Cannabis
The Study at a Glance
Published
Australian Journal of General Practice, 2021
Researchers
University of Sydney (Australia)
Study Type
Systematic ReviewKey Finding
THC impairs driving performance and increases crash risk, with effects lasting 8 hours or more with oral products. Patients should avoid driving during treatment initiation and for several hours or more after each dose.
Key Finding: THC impairs driving performance and increases crash risk, with effects lasting 8 hours or more with oral products. Patients should avoid driving during treatment initiation and for several hours or more after each dose.
What Researchers Studied About This Condition and Cannabis
As medical cannabis use increases, patients need clear guidance on a critical safety question: Can I drive while using medical cannabis?
This 2021 review from Australia examines the scientific evidence on cannabis and driving impairment, providing practical guidance for patients and physicians.
The review addresses both THC and CBD products, and importantly discusses the legal implications of medical cannabis use for driving.
How This Systematic Review Was Conducted
Researchers reviewed the scientific literature on cannabis and driving:
• Examined evidence on THC driving impairment • Assessed crash risk data • Reviewed how long impairment lasts • Discussed legal implications and drug testing
This Condition Treatment Results
The Main Results:
- 1THC impairs driving performance and increases crash risk
- 2Effects are more pronounced in occasional (vs regular) users
- 3Oral cannabis impairment can last 8 HOURS OR MORE
- 4Patients may test positive even when not feeling impaired
- 5Medical cannabis does NOT exempt from roadside drug testing
By the Numbers
| Statistic | What It Means |
|---|---|
| 8+ hours | impairment can last with oral products |
| Not exempt | medical cannabis users from drug testing |
| Higher risk | for occasional vs regular users |
| Avoid | driving during treatment initiation |
impairment can last with oral products
medical cannabis users from drug testing
for occasional vs regular users
driving during treatment initiation
What This Means for This Condition Patients
This review provides critical safety information for medical cannabis patients:
THC and driving - the key facts: • THC DOES impair driving—this is well-established • THC increases crash risk • Effects last longer than you might think: 8 HOURS OR MORE with oral products • Occasional users are MORE impaired than regular users at the same dose
Critical legal issues: • Medical cannabis does NOT exempt you from roadside drug testing • You can test positive for THC even when you don't feel impaired • "Medical necessity" is generally not a legal defense
Safety recommendations: • Avoid driving during treatment initiation when effects are unpredictable • Don't drive for several hours or more after each dose • With oral cannabis products, impairment can last 8 hours or more • Plan transportation accordingly—don't assume you're safe to drive
Quick Answers: This Condition and Cannabis
Direct answers based on the findings of this study:
Research Summary: Answers are based on published peer-reviewed studies and represent research findings, not medical recommendations. Individual results may vary. Always consult a healthcare provider before making treatment decisions.
Can I drive high on weed?
No—cannabis impairs driving and increases crash risk. Wait at least several hours after using. With edibles, impairment can last 8+ hours. Plan a ride or don't use if you need to drive.
Source: McGregor et al., Australian Journal of General Practice, 2021 (PMID: 34059836)
How long after smoking weed can I drive?
Wait several hours or more—edibles can impair you 8+ hours. Occasional users are MORE impaired than regular users at the same dose. When starting medical cannabis, don't drive until you know how it affects you.
Source: McGregor et al., Australian Journal of General Practice, 2021 (PMID: 34059836)
Can I get a DUI with a medical marijuana card?
Yes. A medical card does NOT protect you from DUI charges. You can test positive for THC even when you don't feel high, and "I have a prescription" is not a legal defense in most places.
Source: McGregor et al., Australian Journal of General Practice, 2021 (PMID: 34059836)
This is educational content, not medical advice
The research summarized here is for informational purposes only. Individual results may vary, and what works in studies may not work the same way for everyone. Always consult with a qualified healthcare provider before making changes to your treatment plan or starting medical cannabis therapy.
Important Limitations
This study has some caveats to keep in mind when interpreting the results:
- Review focused on Australian legal context
- Individual impairment varies significantly
- Limited research on long-term medical cannabis users
- Drug testing methods vary by jurisdiction
- Legal landscape is rapidly evolving
The Bottom Line on Cannabis for This Condition
This review delivers essential safety guidance for medical cannabis patients: Cannabis impairs driving and increases crash risk, with effects lasting 8 hours or more with oral products. Patients should not drive during treatment initiation or for several hours or more after each dose. Importantly, having a medical cannabis prescription does NOT exempt patients from roadside drug testing. Plan your transportation accordingly—these findings are critical for any patient using medical cannabis who needs to drive.
Do You Qualify for Medical Marijuana?
If you're living with qualifying condition, you may qualify for a medical marijuana card. Our licensed physicians can evaluate you from home via telehealth.
Related Research & Resources
Related Research
Get Your Card
This condition qualifies for medical marijuana in:
Source
Arkell TR, McCartney D, McGregor IS "Medical cannabis and driving" Australian Journal of General Practice. 2021. DOI: 10.31128/AJGP-02-21-5840
Important Information
Not Medical Advice: This research summary is for educational purposes only. It should not be used to diagnose, treat, cure, or prevent any disease or medical condition. Always consult a qualified healthcare provider before starting or changing any treatment.
Individual Variation: Research findings represent group averages. Your individual response to cannabis may differ based on genetics, other medications, underlying conditions, and many other factors.
Last reviewed: January 24, 2026
Important Notices
Research Summary Disclaimer
This content represents our interpretation of published scientific research for educational purposes. It should not be used to make treatment decisions without consulting a qualified healthcare provider. Individual results may vary from study findings.
FDA Notice
These statements have not been evaluated by the FDA. Cannabis is not intended to diagnose, treat, cure, or prevent any disease. The FDA has not approved cannabis for any medical condition except specific prescription medications.
Copyright & Fair Use
Research summaries are provided under fair use (17 U.S.C. § 107) for educational purposes. We provide brief summaries with attribution, not full reproductions. All studies remain the intellectual property of their respective authors and publishers.
Data Sources
Study information sourced from PubMed®, U.S. National Library of Medicine. Inclusion does not imply endorsement by NLM, NIH, or the federal government.
For complete information, see our Terms of Use and Research Content Policy.
FAQs: Cannabis for This Condition
Can I drive while using medical cannabis?
You should not drive for several hours or more after using cannabis. Cannabis impairs driving and increases crash risk. With oral products, impairment can last 8 hours or more. Plan transportation accordingly.
Does medical cannabis exempt me from DUI testing?
No. Having a medical cannabis prescription does not exempt you from roadside drug testing. You can test positive even when not feeling impaired, and medical necessity is generally not a legal defense.
How long should I wait to drive after using cannabis?
With oral cannabis products, impairment can last 8 hours or more. Smoked/vaped cannabis has shorter duration but still causes impairment. Avoid driving entirely during treatment initiation when effects are unpredictable.