What is the legal THC limit for driving?

There is no national standard. States use three approaches: per se limits (Colorado, Washington, Montana, Illinois at 5 ng/mL blood; Nevada and Ohio at 2 ng/mL), zero tolerance (Michigan for recreational users, Oklahoma — any detectable THC is illegal), and impairment-based (Oregon, Maine, Missouri — no specific limit, impairment must be proven).

Can you get a DUI for cannabis used days ago?

Yes, in per se and zero-tolerance states. THC is fat-soluble and metabolites persist for days or weeks after use. A daily cannabis user can have blood THC levels above 5 ng/mL for up to 7 days after stopping, and detectable metabolites for 30+ days. In zero-tolerance states like Oklahoma, any detectable amount equals a DUI charge.

How long should you wait to drive after using cannabis?

Wait at minimum 4-6 hours after inhaling cannabis and 8+ hours after edibles. Peak impairment from inhalation occurs within 30 minutes and diminishes over 2-4 hours. Edibles produce effects lasting 4-8+ hours. These are minimums — waiting longer is safer, and daily users should be aware that residual THC may exceed per se limits even after waiting.

Does a medical card protect you from a cannabis DUI?

In most states, no. A medical card does not exempt you from DUI laws. Notable exceptions: Michigan's People v. Koon (2013) ruling established that medical patients cannot be convicted solely on THC presence — impairment must be proven. In Oklahoma, a medical card is explicitly NOT a defense against DUI charges.

What happens if you get a cannabis DUI while traveling?

An out-of-state cannabis DUI follows you home. It will appear on your driving record, affect your insurance rates, and can impact employment nationwide. Penalties vary by state but typically include jail time (up to 1 year for first offense), fines ($375-$6,250), and license suspension (90 days to 3 years).

Why is the 5 ng/mL THC limit controversial?

Unlike the well-established 0.08% BAC alcohol threshold, there is no scientific consensus that 5 ng/mL blood THC reliably indicates impairment. Chronic users can exceed this level days after use when no longer impaired. Some states like Nevada use an even lower 2 ng/mL threshold, which regular users may exceed the morning after use.

Cannabis DUI Laws by State — Limits & Penalties

Legal Disclaimer: This information reflects Global cannabis law as of March 2026 and is for educational purposes only. It is not legal advice. Laws and regulations change — always verify current rules with the Multiple International Authorities or a qualified attorney. Cannabis remains illegal under federal law.

Last verified: March 2026

Universal Rule: Never carry cannabis across any international border — even between two legal countries. This is a serious criminal offense everywhere on Earth, with no exceptions. Read more →

If you use cannabis and drive in the United States — even in states where cannabis is fully legal — you face a patchwork of DUI laws that can vary dramatically between one state and the next. A THC blood level that is legal in Oregon could get you arrested in Nevada. A medical card that protects you in Michigan means nothing in Oklahoma.

This page covers the three approaches states use for cannabis DUI enforcement, a state-by-state comparison table, the metabolite problem that affects daily users and travelers, and practical guidance for staying safe and legal.

Three Approaches to Cannabis DUI Laws

States generally fall into one of three categories when it comes to detecting and prosecuting cannabis-impaired driving:

1. Per Se Limits (Specific THC Threshold)

These states set a legal limit for THC in blood, similar to the 0.08% BAC limit for alcohol. If your blood THC level exceeds the threshold, you are considered impaired by law — regardless of whether you actually appear impaired. This is the most straightforward approach, but it has significant problems (more on that below).

2. Zero Tolerance (Any Detectable THC)

Critical Safety Warning: Zero-tolerance states will prosecute you for any detectable amount of THC or THC metabolites in your system. This means you can be charged with DUI days or even weeks after your last cannabis use, long after any impairment has passed. Daily users are essentially always in violation in these states.

3. Impairment-Based (No Specific THC Limit)

These states do not set a specific THC limit. Instead, prosecutors must prove actual impairment through evidence like field sobriety tests, officer observations, dash cam footage, and Drug Recognition Expert (DRE) evaluations. This approach is arguably more fair — you are only prosecuted if you were actually impaired — but it is also more subjective and can depend heavily on the arresting officer's judgment.

State-by-State Cannabis DUI Laws

The following table covers key legal and recreational cannabis states. Laws change frequently — always verify current law before traveling.

State	Approach	THC Limit	First Offense Penalty	Medical Exemption?
Colorado	Per se (permissible inference)	5 ng/mL blood	Up to 1 year jail, $600–$1,000 fine, 9-month license suspension	No — medical patients held to same standard
Washington	Per se	5 ng/mL blood	Up to 364 days jail, $5,000 fine, 90-day license suspension	No — 5 ng/mL applies to all drivers
Montana	Per se	5 ng/mL blood	Up to 6 months jail, $600–$1,000 fine, 6-month license suspension	No
Illinois	Per se	5 ng/mL blood (or 10 ng/mL other bodily substance)	Up to 1 year jail, up to $2,500 fine, 1-year license revocation	No
Nevada	Per se	2 ng/mL blood	2 days–6 months jail (or 48–96 hours community service), $400–$1,000 fine	No — one of the strictest limits in the country
Ohio	Per se	2 ng/mL blood (or 15 ng/mL urine)	3 days–6 months jail, $375–$1,075 fine, 1–3 year license suspension	Limited — medical patients can argue affirmative defense
Oregon	Impairment-based	No per se limit	Up to 1 year jail, $6,250 fine, 1-year license suspension	N/A — impairment must be proven
Maine	Impairment-based	No per se limit	Up to 364 days jail, $500–$2,000 fine, 150-day license suspension	N/A — impairment must be proven
Michigan	Zero tolerance (recreational); case law exemption for medical	Any detectable THC	Up to 93 days jail, $500 fine, up to 180-day license suspension	Yes — People v. Koon (2013) established that medical patients cannot be convicted solely on the presence of THC; impairment must be proven
Oklahoma	Zero tolerance	Any detectable amount	Up to 1 year jail, up to $1,000 fine, license revocation	No — medical card is not a defense against DUI
Missouri	Impairment-based (constitutional protection)	No per se limit	Up to 6 months jail, up to $500 fine	N/A — Amendment 3 (2022) provides constitutional protection; impairment must be proven

The Nevada and Ohio 2 ng/mL limits are extremely low. For context, a regular cannabis user could exceed 2 ng/mL the morning after use, well after impairment has passed. If you are driving through Nevada after visiting a legal dispensary in Las Vegas, be aware that the per se limit is stricter than neighboring states.

Why This Matters for Travelers

This is a travel safety guide, and the state-by-state variation in cannabis DUI laws creates real risks for people driving between legal states.

You drive through multiple jurisdictions. A road trip from Portland, Oregon (no per se limit) through Nevada (2 ng/mL per se limit) subjects you to Nevada's laws the moment you cross the state line. You do not get to use Oregon's more favorable standard.
Legal cannabis use in one state can equal a DUI in the next. Using cannabis legally at your hotel in Colorado on Saturday night could mean exceeding Nevada's 2 ng/mL threshold when you drive through on Sunday. You would not be impaired, but you would be in technical violation.
Zero-tolerance states are worst for travelers. If you are a regular cannabis user passing through Oklahoma or Michigan (for recreational users), any detectable THC in your blood means a DUI charge — regardless of when you last used.
Out-of-state DUI charges follow you home. A cannabis DUI in any state will appear on your driving record, affect your insurance, and potentially impact your employment nationwide.

The Metabolite Problem

This is the fundamental flaw in most per se and zero-tolerance cannabis DUI laws: THC metabolites persist in the body long after impairment ends.

Unlike alcohol, which is metabolized and eliminated from the body within hours, THC is fat-soluble. After use, THC is stored in fat cells and slowly released as metabolites (primarily THC-COOH) over days or weeks. For daily users, detectable metabolites can persist for 30 days or more after complete abstinence.

This creates a fundamental problem for law enforcement and justice:

A daily user who last consumed cannabis three days ago may have a blood THC level above 5 ng/mL without any current impairment.
Some states test for THC-COOH (the inactive metabolite) rather than active delta-9-THC, meaning they are detecting past use rather than current impairment.
There is no scientific consensus on what blood THC level reliably indicates impairment. Unlike the well-established 0.08% BAC threshold for alcohol, the 5 ng/mL THC standard is based on limited evidence.

For details on how long THC stays in your system by test type, see our Drug Testing Timelines page.

A study published in <em>Clinical Chemistry</em> found that chronic cannabis users can maintain blood THC levels above 5 ng/mL for up to 7 days after cessation, and one participant maintained levels above 2 ng/mL for more than 30 days. The researchers concluded that a single blood THC concentration cannot reliably indicate the time of cannabis use or degree of impairment.
Bergamaschi et al. — Impact of Prolonged Cannabinoid Excretion in Chronic Daily Cannabis Smokers, Clinical Chemistry, 2013

Practical Advice for Travelers

Regardless of what the legal limits are, the most important rule is simple: do not drive impaired. Beyond that, here are specific recommendations for travelers:

After inhaling cannabis: Wait a minimum of 4 to 6 hours before driving. Peak impairment occurs within 30 minutes of inhalation and diminishes over 2 to 4 hours, but residual effects can last longer.
After edibles: Wait a minimum of 8 hours, and longer for higher doses. Edibles produce longer-lasting effects (4 to 8+ hours), and impairment from a high dose can persist well beyond the subjective experience of being "high."
Know the laws before you drive through a state. If your road trip route passes through a zero-tolerance state, factor that into your planning. The laws in your destination may be more permissive than the states along the way.
Do not consent to a roadside blood test without understanding the implications. In many states, implied consent laws mean that refusing a blood or breath test results in automatic license suspension. But consenting to a blood test when you have detectable metabolites from legal use days ago can result in a DUI charge. This is a situation where knowing your rights matters.
Keep cannabis products in the trunk. An open package of cannabis in the passenger area can constitute an "open container" violation in many states, similar to open alcohol containers.

The safest approach: Treat cannabis like alcohol — use it at your destination, not before or during driving. Wait significantly longer than you think necessary. And if you are a daily user driving through zero-tolerance states, understand that you may technically be in violation even if you have not used cannabis in days.

For state-specific cannabis law details, visit our partner sites: WashingtonCannabis.org, CannabisMichigan.org, CannabisOregon.org, CannabisMaine.org. For information on how long THC stays in your system, see TryCannabis.org's Drug Testing Guide.