Marijuana DUI Laws by State: THC Limits and Driving Laws in 2026

Marijuana DUI laws vary significantly from state to state. While every state prohibits driving while impaired by marijuana, only a handful use a specific THC concentration as a legal limit.

Most states instead require prosecutors to prove that marijuana impaired a person’s ability to drive. Other states use zero-tolerance or “any amount” laws that can make it illegal to drive with detectable THC or certain marijuana metabolites in the body under specified circumstances.

There is no nationwide marijuana equivalent to the 0.08% blood alcohol concentration standard used for alcohol.

The table below compares marijuana DUI laws in all 50 states and the District of Columbia, including states with THC blood limits, zero-tolerance rules and impairment-based standards.

For broader information on possession, legalization, home cultivation, medical marijuana and sales, visit The Marijuana Herald’s Marijuana Laws by State guide.

National summaries maintained by the Governors Highway Safety Association show that most states continue to rely on impairment rather than a numerical marijuana limit, while a smaller group use per se, zero-tolerance or any-amount standards. Current statutes are especially important because older national charts can miss changes or exceptions created by legalization.

Only a small number of states use a specific THC concentration as a per se driving limit.

Washington uses a limit of 5 ng/mL of THC in whole blood when measured within two hours of driving. Illinois also uses a 5 ng/mL whole-blood threshold, along with a 10 ng/mL threshold for other bodily substances. Montana uses a 5 ng/mL blood threshold.

Ohio uses one of the country’s lower THC thresholds, with a limit of 2 ng/mL in whole blood, blood serum or plasma and 10 ng/mL in urine.

Colorado is different. A blood THC concentration of at least 5 ng/mL creates a “permissible inference” that a driver was under the influence. That means the result can be used as evidence of impairment, but it does not automatically establish guilt.

Nevada is another important exception. The state previously had general numerical marijuana limits, but its 2 ng/mL delta-9 THC and 5 ng/mL 11-hydroxy-THC thresholds now apply in specified felony DUI cases rather than serving as a general per se standard for every marijuana DUI.

No.

Although several states use 5 ng/mL of THC in some form, there is no nationally accepted THC concentration equivalent to the 0.08% blood alcohol concentration standard.

Alcohol and THC behave differently in the body. Blood alcohol concentration has a comparatively established relationship with alcohol consumption and impairment. THC concentrations can rise quickly after marijuana use and then decline rapidly, and the relationship between a particular THC concentration and a person’s level of impairment is less straightforward.

That is one reason most states have not adopted a universal numerical THC limit.

Federal highway-safety research has also cautioned against treating a particular THC concentration as a direct equivalent to a blood alcohol concentration.

Yes.

A THC limit does not necessarily create a safe harbor below that number.

Washington, for example, allows evidence of a THC concentration below 5 ng/mL to be considered along with other evidence when determining whether a person was under the influence of marijuana.

Similarly, states with impairment-based DUI laws do not need a driver to reach any particular THC concentration. A prosecutor may instead rely on the driver’s behavior, observations by law enforcement, performance on field sobriety tests, toxicology results, statements about marijuana consumption and other evidence.

A driver therefore should not assume that being below 5 ng/mL, or any other numerical level, means it is legal to drive.

Several states take an approach that is stricter than a numerical impairment limit.

These laws generally prohibit driving with THC or specified marijuana metabolites in the body, although the exact language and available defenses differ substantially by state.

Indiana, Iowa, Oklahoma, Pennsylvania, Rhode Island, Utah and Wisconsin are among states with zero-tolerance or any-amount provisions relevant to marijuana driving. Arizona and Georgia also have broad drug-presence provisions, although Arizona law includes important limitations involving metabolites and protections for registered medical marijuana patients.

These statutes should not all be treated as identical. Some apply to active THC, some include metabolites, some contain medical-use defenses or exceptions, and others operate alongside separate impairment-based DUI laws.

Pennsylvania, for example, prohibits driving with any amount of a Schedule I controlled substance or its metabolite in the blood and separately prohibits driving while under the influence of a drug to a degree that impairs safe driving.

Minnesota is particularly important because some older state-by-state DUI charts identify it as a marijuana zero-tolerance state.

Current Minnesota law expressly excludes cannabis flower, cannabis products, lower-potency hemp edibles, hemp-derived consumer products, artificially derived cannabinoids and tetrahydrocannabinols from the provision making it illegal to drive with any amount of certain Schedule I or II substances in the body.

Marijuana DUI cases in Minnesota instead generally depend on evidence that the driver was under the influence.

For most adult drivers, South Dakota uses an impairment standard.

State law prohibits operating a vehicle while under the influence of marijuana to the extent that a person is incapable of safely driving.

However, South Dakota has a separate rule for people younger than 21. A person under 21 may not drive after consuming marijuana while physical evidence of that consumption remains present in the person’s body.

This distinction is another reason simple national lists of “zero-tolerance states” can be misleading.

In a state without a numerical THC threshold, the central question is generally whether marijuana affected the driver’s ability to safely operate a vehicle.

Law enforcement and prosecutors may rely on a combination of driving behavior, the circumstances surrounding a traffic stop or crash, physical observations, field sobriety testing, toxicology testing, statements from the driver and testimony from officers or drug-recognition experts.

A positive marijuana test does not necessarily answer when marijuana was consumed or how impaired a particular driver was at the time. The legal significance of a toxicology result therefore depends heavily on the state’s statute and the other evidence in the case.

No.

Legalizing possession or recreational marijuana does not make it legal to drive while impaired.

The same principle applies to medical marijuana patients. A medical marijuana card authorizes marijuana use within the boundaries of a state’s medical program, but it does not authorize impaired driving.

Some states do provide medical patients with protections from an automatic drug-presence violation. Arizona, for example, provides statutory protections related to the presence of marijuana components or metabolites when concentrations are insufficient to cause impairment, while Illinois’ per se THC provision contains an exception relating to lawful medical marijuana use.

A medical authorization therefore may matter under a particular statutory provision, but it is not a defense to actually driving while impaired.

Potentially, but the answer depends on whether the person is impaired and on the law of the state.

There is no nationwide rule establishing that a person can legally drive a specific number of hours after using marijuana.

THC levels and impairment can be affected by the method of consumption, dose, product potency, frequency of use and individual differences. Edible marijuana products can also have a different onset and duration than inhaled marijuana.

In a zero-tolerance or any-amount state, detectable THC or a prohibited metabolite may create additional legal concerns even when a driver does not feel impaired.

The safest legal approach is not to drive while experiencing the effects of marijuana.

Generally, state DUI laws focus on impairment or THC in the body rather than whether the marijuana was smoked, vaporized or eaten.

A person can therefore receive a marijuana DUI after consuming an edible just as they can after smoking marijuana.

Edibles can create a particular risk because their effects may take longer to begin and may last longer than the effects associated with inhaled marijuana. There is no separate exemption simply because the marijuana was consumed as food or a beverage.

Legal possession and impaired driving are separate issues.

In states where marijuana possession is legal, an adult may generally transport marijuana within applicable possession limits, but vehicle-storage and open-container restrictions may apply.

A person can therefore legally possess marijuana while still violating another law if the product is open, improperly stored or being consumed inside the vehicle.

Possessing marijuana legally also does not provide any protection for driving while impaired.

For state-specific possession rules, see our Marijuana Laws by State guide.

There is no nationwide legal THC limit. Most states do not use a numerical THC threshold at all. States that do use numerical standards vary, with limits including 2 ng/mL and 5 ng/mL depending on the state and circumstances.

Washington, Illinois and Montana use 5 ng/mL of delta-9 THC in blood as part of their marijuana-driving laws. Colorado uses 5 ng/mL as the threshold for a permissible inference of impairment rather than a strict automatic per se violation.

Yes. Every state prohibits driving while impaired by marijuana regardless of whether recreational or medical marijuana is legal.

Yes. In states such as Washington, a THC concentration below the per se limit can still be considered alongside other evidence of impairment. States without numerical limits may prosecute marijuana DUI entirely on evidence of impairment.

No. Medical marijuana patients are prohibited from driving while impaired. Some states provide medical patients with protections from certain automatic drug-presence provisions, but those protections do not legalize impaired driving.

No. Unlike the nationwide 0.08% alcohol standard for most adult drivers, marijuana DUI standards are determined by individual states.

Potentially. A marijuana DUI investigation may involve observations of impairment and other evidence even when a numerical THC result is unavailable. The evidence required for conviction depends on state law and the facts of the case.

Marijuana DUI laws can change through legislation, court decisions and regulatory changes. The Marijuana Herald regularly reviews this guide to reflect changes in state law.

This guide provides a general overview of marijuana driving laws and is not legal advice. DUI statutes are highly fact-specific, and additional rules may apply to drivers younger than 21, commercial drivers, medical marijuana patients, repeat offenders and cases involving crashes or injuries.

For detailed information on marijuana possession, cultivation, medical access, sales and penalties in individual states, visit The Marijuana Herald’s Marijuana Laws by State guide.

This guide was compiled using current state statutes and official government resources, including:

Because marijuana DUI laws can change through legislation and court rulings, readers should consult the current statute in their state for the most up-to-date requirements.