Missouri allows qualified patients to possess medical marijuana legally. However, if you drive after consuming marijuana—even with a valid card—you can face criminal charges. Missouri law treats driving while impaired by any substance as illegal, and that includes marijuana. If an officer believes you show signs of impairment, they can arrest you for driving while intoxicated (DWI).
Can THC in your system lead to a DWI?
Missouri prohibits driving while under the influence of marijuana and this includes medical cannabis. Law enforcement and prosecutors often look at a person’s intoxicated condition by impairment, not THC levels. Although 5 ng/mL is not a legal limit in Missouri, authorities typically treat it as a de facto indicator of impairment.
How does law enforcement determine impairment?
Officers look for signs such as drifting between lanes, delayed reactions or confusion. They perform field sobriety tests and request blood or urine samples. Because Missouri follows an implied consent law, officers can require drivers arrested for driving while intoxicated (DWI) to take a chemical test. Prosecutors then use the test results and officer observations to build their case.
Does a medical marijuana card offer protection?
Missouri’s constitution makes it clear that no one, including registered patients, can legally drive while impaired by marijuana. A card does not excuse impaired driving.
What should patients know about timing?
THC can remain in your bloodstream for a long time after the effects wear off. Studies show that test results can still register above certain levels more than 12 hours later. Since no official waiting period exists, it is advisable to avoid driving until you feel fully alert and capable.
Stay safe and legal
If you are a medical marijuana patient in Missouri, knowing the limits of the law is just as important as knowing your rights. Take the following steps to protect yourself:
- Avoid driving if you feel even mildly impaired.
- Schedule travel based on your treatment times.
- If you face charges, question the testing method and timing.
When you stay informed and cautious, you lower your risk of serious legal trouble. Missouri enforces its driving laws, particularly when public safety is at risk.
Final thoughts on DWI in Missouri
Medical marijuana is legal in Missouri but driving while impaired is not. The state takes DWI charges seriously—even for registered patients. Missouri law did not set a THC limit; thus, law enforcement focuses on behavior and test results. Staying informed can help protect both your freedom and public safety.