Colorado Marijuana Driving Laws: THC Limits, DUI, and Penalties

Colorado’s marijuana driving laws make it illegal to operate a vehicle while impaired by cannabis, and the state sets a benchmark of five nanograms of active delta-9 THC per milliliter of blood as the point where a jury may presume you were impaired. You can still be arrested and convicted below that number if an officer observes signs of impairment, and even a first conviction carries mandatory jail time. Medical marijuana patients get no special treatment behind the wheel.

The Five-Nanogram THC Threshold

Colorado law creates what’s called a “permissible inference” of impairment when a driver’s blood contains five or more nanograms of delta-9 THC per milliliter of whole blood.¹ Unlike alcohol’s hard 0.08 BAC cutoff, that THC number doesn’t automatically make you guilty. It allows a jury or judge to conclude you were impaired based on the reading alone, and you can still challenge the inference with other evidence.²

What catches many drivers off guard is that you don’t need to reach five nanograms to get charged. If your driving ability is affected to even the slightest degree, you can be arrested for DUI or DWAI regardless of your blood-THC reading.³ Officers regularly pursue cases against drivers with THC levels well below the threshold when field observations point to impairment.

The five-nanogram standard applies specifically to delta-9 THC. Other cannabinoids such as delta-8 aren’t measured under that benchmark, but Colorado’s general impairment statutes cover any substance affecting your ability to drive. If delta-8, an edible, or any other cannabis product impairs you to the slightest degree, you face the same charges.³

DUI and DWAI: Two Levels of Charge

Colorado splits marijuana driving offenses into two categories depending on how impaired you were. DUI carries heavier penalties, but neither charge is minor. Both go on your criminal record, and both count toward the repeat-offense thresholds that eventually trigger felony charges.

A DUI, or Driving Under the Influence, applies when marijuana has affected you enough that you’re substantially unable to drive safely, meaning your judgment, physical control, or reaction time is seriously compromised.¹

A DWAI, or Driving While Ability Impaired, is a lower bar. You face this charge if marijuana has affected your driving ability to the “slightest degree,” making you even marginally less capable than you’d normally be.¹ That phrase is not an exaggeration. Prosecutors don’t need to show you were swerving or driving dangerously; they just need evidence you were less sharp than usual.

How Officers Test for Marijuana Impairment

Breathalyzers can’t detect THC, so blood draws are the primary testing method. Colorado law also allows officers to collect saliva and urine samples to determine drug content.⁴ The officer must obtain the sample within two hours of the time you were driving. Many departments also use specially trained Drug Recognition Experts who follow a standardized twelve-step evaluation protocol covering eye movement, divided-attention tests, vital signs, and pupil size.⁵ Results from a DRE evaluation often serve as the foundation of a prosecution even before blood test results come back.

Express Consent and the Cost of Refusing

Under Colorado’s express consent law, anyone driving on Colorado roads is considered to have already consented to chemical testing when an officer has probable cause to suspect impairment.⁴ You may decline voluntary roadside coordination exercises, but refusing the chemical test itself triggers administrative penalties entirely separate from any criminal case:

First refusal: one-year license revocation
Second refusal: two-year license revocation
Third refusal: three-year license revocation⁶

A refusal also requires you to use an ignition interlock device for two years after reinstatement and to enroll in a Level II alcohol and drug education program.⁷ These consequences apply whether or not you’re ultimately convicted of the underlying DUI. Refusing doesn’t help you avoid conviction either: prosecutors can introduce the refusal as evidence of consciousness of guilt.

First-Offense Penalties

A first marijuana DUI in Colorado carries mandatory jail time. The penalties differ depending on whether you’re convicted of DUI or the lesser DWAI.

A first DUI is a misdemeanor punishable by five days to one year in jail with a five-day mandatory minimum, fines of $600 to $1,000, 48 to 96 hours of community service, up to two years of probation, and 12 points added to your driving record.²

A first DWAI is also a misdemeanor, with lighter but still significant penalties: two to 180 days in jail with a two-day mandatory minimum, fines of $200 to $500, 24 to 48 hours of community service, up to two years of probation, and 8 points on your driving record.²

These numbers don’t capture the full financial hit. Court-ordered substance abuse education, attorney fees, and the insurance premium increases that follow a conviction typically add thousands of dollars beyond the statutory fines. After a DUI-related revocation, Colorado typically requires an SR-22 insurance filing for three years from the date you become eligible for reinstatement, and SR-22 coverage generally costs significantly more than a standard policy.

Point totals matter on their own. For drivers 21 and older, accumulating 12 or more points within any 12-month period, or 18 within 24 months, triggers an automatic license suspension.⁸ A single first-offense DUI conviction can independently trigger a point suspension on top of any other license action from the criminal case, though administrative and criminal revocations arising from the same incident run concurrently.⁶

Repeat Offenses and Felony DUI

Penalties escalate sharply with each subsequent conviction. Colorado counts prior DUI, DWAI, vehicular assault, and vehicular homicide convictions from any state toward the repeat-offense thresholds.¹

A second offense carries 10 days to one year in jail with a 10-day mandatory minimum, fines of $600 to $1,500, 48 to 120 hours of community service, and a one-year license revocation. A third offense carries 60 days to one year in jail with a 60-day mandatory minimum, the same fine and community service ranges, at least 90 days of continuous alcohol monitoring, and a five-year license revocation under the habitual traffic offender statute if the three convictions fall within seven years.²

A fourth DUI or DWAI becomes a class 4 felony.¹ Felony DUI carries potential prison time rather than county jail, a permanent felony record, and the loss of certain civil rights.

Open Marijuana Container Rules

Colorado prohibits open marijuana containers in the passenger area of a vehicle, but the legal definition of “open container” is narrower than most people assume. All three of these conditions must be true at the same time: the container is open or its seal is broken, some of the product has been removed, and there’s evidence marijuana was consumed inside the vehicle.⁹

Simply having a previously opened package in your car doesn’t automatically trigger a violation. That said, the smell of burnt marijuana inside a car can serve as evidence of in-vehicle consumption during a traffic stop, so the practical protection of this three-part test is thinner than it appears on paper.

The rules apply to everyone in the vehicle. Neither drivers nor passengers can open cannabis packaging or consume any cannabis product in a vehicle, even when parked.³ If your vehicle has a trunk, store any previously opened containers there. Without a trunk, place them behind the last upright seat in an area not normally occupied by passengers.⁹

Medical Marijuana Is Not a Defense

Colorado’s statute explicitly states that being legally entitled to use marijuana, including under a medical marijuana card, is not a defense to impaired driving charges.¹ The same five-nanogram threshold and the same penalties apply to every driver regardless of prescription status.³

This creates a real problem for daily medical users. Regular cannabis consumers can maintain detectable THC blood levels long after the impairing effects have worn off. A medical patient who used marijuana the previous evening could still test above five nanograms the next morning. The permissible inference at that threshold then shifts the practical burden onto the driver to convince a jury they weren’t actually impaired, which is a harder position to argue from than starting at zero.

1
Justia Law. Colorado Code 42-4-1301 – Driving Under the Influence – Driving While Impaired – Driving With Excessive Alcoholic Content – Definitions – Penalties
2
Colorado General Assembly. Colorado Law Summary: Colorado Drunk Driving Laws
3
Colorado Department of Revenue. Driving and Traveling
4
Justia Law. Colorado Code 42-4-1301.1 – Expressed Consent for the Taking of Blood, Breath, Urine, or Saliva Sample
5
International Association of Chiefs of Police. 12 Step Process
6
Justia Law. Colorado Code 42-2-126 – Revocation of License
7
Colorado Department of Revenue. Express Consent
8
Colorado Department of Revenue. Point Suspensions
9
Justia Law. Colorado Code 42-4-1305.5 – Open Marijuana Container