Last verified: March 2026

The 5 ng/mL THC Standard

Colorado law establishes a 5 ng/mL THC permissible inference for driving under the influence. This is not a "per se" limit like alcohol's 0.08 BAC — it creates a rebuttable presumption of impairment. If your blood THC level is at or above 5 ng/mL, a jury may infer that you were impaired, but you can present evidence to the contrary.

The AAA Foundation for Traffic Safety found no reliable correlation between THC blood levels and actual impairment, but the 5 ng/mL standard remains Colorado law and has been adopted or influenced standards in Washington, Montana, Nevada, and Ohio.

CDOT Recommendations

The Colorado Department of Transportation recommends:

• Wait at least 6 hours after smoking or vaping before driving
• Wait at least 8 hours after consuming edibles before driving
• Heavy or daily consumers should be aware that THC can remain in the blood well above 5 ng/mL even hours after last use
• When in doubt, use a rideshare, taxi, or designated driver

Open Container Laws

Colorado prohibits open cannabis containers in the passenger area of a vehicle, similar to open alcohol container rules. Cannabis products must be in a sealed container or the trunk. An opened, partially consumed package in the center console or passenger seat can result in an open container citation.

DUI Penalties

Colorado also recognizes DWAI (Driving While Ability Impaired) as a lesser included offense. DWAI applies when you are affected to the slightest degree — even if blood THC is below 5 ng/mL.