Legal Alcohol Limit in Colorado: DUI, DWAI, and Refusal Penalties

The legal alcohol limit in Colorado is a blood alcohol content of 0.08% for most adult drivers. Hit that number and you can be charged with driving under the influence (DUI) on the BAC alone, without any additional proof that your driving was affected. Colorado also draws a second, lower line at 0.05%, and the cutoffs drop further for commercial drivers and anyone under 21.¹

The Two Lines for Adult Drivers

Colorado’s DUI statute sets two thresholds, not one. A BAC of 0.08% or higher at the time of driving, or within two hours after, is DUI per se. “Per se” means the number is enough by itself; prosecutors don’t have to show your driving suffered.¹

The second line sits at 0.05%. A BAC between 0.05% and just under 0.08% creates what the statute calls a “permissible inference” of impairment. That supports a charge of driving while ability impaired (DWAI), a separate and lesser offense than DUI, but still criminal.¹

At or below 0.05%, the law presumes you were not impaired by alcohol. That presumption can be rebutted with other evidence, but a BAC in that range rarely produces an alcohol charge on its own.

Lower Limits for Commercial and Underage Drivers

Commercial driver’s license holders operate under a stricter number. A BAC of 0.04% while driving a commercial vehicle is what Colorado calls “excess BAC CDL.” A conviction revokes commercial driving privileges for the disqualification periods set by federal rule: at least one year for a first offense and a lifetime disqualification for a second. Hauling hazardous materials pushes the first-offense disqualification to three years.²

Drivers under 21 face the tightest limit. Any BAC from 0.02% up to 0.05% is a class A traffic infraction, and a court can order up to 24 hours of community service plus an alcohol evaluation or education program at the young driver’s expense. A second violation is a class 2 traffic misdemeanor. Once an underage driver reaches 0.05% or higher, the regular adult DUI and DWAI charges apply.¹

Drugs, Including Marijuana

The same law covers drugs. You can be charged with DUI or DWAI for driving under the influence of any drug, including prescription medication, marijuana, or a mix of alcohol and drugs.¹

For marijuana, five nanograms or more of active Delta-9 THC per milliliter of whole blood creates the same permissible inference of impairment that 0.08% BAC creates for alcohol. But officers can arrest and charge below five nanograms if they document impaired driving behavior. A valid prescription or a legal purchase does not shield you from a drugged driving charge if the substance affected your ability to drive.³

Penalties for a First Offense

A first DUI is a misdemeanor. The criminal penalties run from 5 days to 1 year in jail, a fine of $600 to $1,000, and 48 to 96 hours of community service. Administratively, a first DUI adds 12 points to your driving record and triggers a 9-month license revocation.⁴

A first DWAI is also a misdemeanor, with lighter penalties: 2 to 180 days in jail, a fine of $200 to $500, and 8 points on your record. A first DWAI does not carry an automatic license revocation on the BAC alone, though the 8 points can contribute to a suspension when stacked with other violations.⁴

Both offenses come with additional costs on top of the fine: court costs, a surcharge of up to $500 for persistent-drunk-driver programs, a crime victim compensation fund surcharge, and license reinstatement fees. A judge may suspend part of the minimum jail sentence if you agree to complete an alcohol treatment program.⁴

Penalties climb sharply with each prior conviction, and a fourth DUI, DUI per se, or DWAI becomes a class 4 felony carrying 2 to 6 years in state prison. Prior vehicular homicide and vehicular assault convictions count toward that trigger.¹

The 0.15% Trap: Persistent Drunk Driver

Colorado has a separate label that can apply on a first offense. You can be classified a “persistent drunk driver” if any one of these is true: your BAC was 0.15% or higher, you have two or more alcohol-related driving convictions or license revocations, you drove while your license was already restricted for an alcohol offense, or you refused a chemical test.⁴

The label matters. A persistent drunk driver faces a two-year ignition interlock requirement instead of the nine months attached to a standard first DUI, and must enroll in a Level II alcohol education and treatment program before getting a license back.⁵ The 0.15% cutoff catches a lot of first-time drivers off guard, because a single heavy night can land you in a category that sounds like it was built for repeat offenders.

Refusing a Test: Expressed Consent

Colorado uses “expressed consent.” By driving on any road in the state, you are considered to have already consented to a breath or blood test whenever an officer has probable cause to believe you’re driving impaired. The officer can also request a blood, saliva, or urine test if drugs are suspected. The sample has to be taken within two hours of driving.⁶

You can refuse. The consequences are steep. A first refusal triggers a 12-month license revocation, a second triggers 24 months, and a third triggers 36 months. After reinstatement, you face a two-year ignition interlock requirement and have to show enrollment in a Level II alcohol education program. SR-22 insurance may also be required. And refusal on its own qualifies you as a persistent drunk driver, pulling in the added consequences described above.⁷

1
Justia. Colorado Code 42-4-1301 – Driving Under the Influence, Driving While Impaired, Driving With Excessive Alcoholic Content, Definitions, Penalties
2
FindLaw. Colorado Code 42-2-126 – Revocation of License Based on Administrative Determination
3
CDOT. Drugged Driving Frequently Asked Questions
4
Colorado General Assembly. Colorado Drunk Driving Laws – Colorado Law Summary
5
Colorado Division of Motor Vehicles. Ignition Interlock Program
6
FindLaw. Colorado Code 42-4-1301.1 – Expressed Consent for the Taking of Blood, Breath, Urine, or Saliva Sample, Testing, Fund, Rules, Repeal
7
Colorado Department of Revenue. Express Consent