Yes. Daily or long-term marijuana users are more likely to test above Washington’s legal THC limit—even when they don’t feel impaired. Under RCW 46.61.502, drivers with 5 nanograms of active THC per milliliter of blood within two hours of driving can be charged with a marijuana DUI.
For a fuller picture of how these cases are defended, see our marijuana DUI defense page.
THC is fat-soluble, meaning it builds up in body fat and releases slowly over time. Because of this, habitual users can maintain measurable levels of active THC for many hours after use. Someone who smokes daily could still test above the legal limit even if they haven’t consumed cannabis since the previous night.
Having a medical marijuana authorization card does not exempt anyone from DUI laws. It only affects possession limits, not impairment standards. If a blood test shows 5 ng/mL or higher—or if an officer observes signs of impairment—a DUI charge can follow.
For frequent users, the safest approach is to allow plenty of time between use and driving. Even though cannabis is legal in Washington, driving with active THC above the legal threshold remains a criminal offense.
If you need help applying this to your specific facts, contact our office.