Driving under the influence of cannabis is illegal in all 50 states, even in states where cannabis is legal to possess and use

Cannabis impairs the same skills you need to drive safely: reaction time, attention, and judgment. Every state treats driving high the same way it treats driving drunk — as a criminal offense. The fact that cannabis is legal in your state for personal use does not make it legal to drive after using it. Police can arrest you, you can lose your license, and you can face jail time and fines.

The challenge for law enforcement is that there is no roadside breath test for cannabis the way there is for alcohol. Instead, officers use observation, field sobriety tests, and blood or urine tests to build a case. A positive test does not always prove impairment at the moment of driving — cannabis can stay in your system for days or weeks — but many states have set legal limits anyway, and exceeding them is enough for a conviction.

Key Takeaways

  • Driving high is illegal in all states and is prosecuted as impaired driving, regardless of whether cannabis is legal in your state.
  • Police do not need a breath test to arrest you; they can use observation, field sobriety tests, and blood or urine results as evidence.
  • Many states have set a legal limit for THC in your blood (commonly 2 to 5 nanograms per milliliter), and exceeding it can result in a conviction even if you feel fine.
  • A conviction for driving high carries penalties including license suspension, fines, jail time, and a permanent criminal record that affects employment and housing.
  • The only safe choice is to wait several hours after using cannabis before driving, or to use a taxi, rideshare, or designated driver.

How Police Detect Cannabis Impairment

An officer who suspects you are driving high will look for signs during a traffic stop: slow reaction to lights or sirens, weaving between lanes, difficulty following instructions, or an odor of cannabis in the car. They may ask you to perform field sobriety tests — walking a straight line, standing on one leg, or following a pen with your eyes — the same tests used for alcohol impairment.

If the officer believes you are impaired, they can arrest you and request a blood or urine test at a police station or hospital. A blood test is more common because it can measure the level of THC (the active ingredient in cannabis) in your system. Some states also allow saliva tests, though these are less reliable. The results are then used as evidence in court.

Unlike alcohol, where a breath test gives an when ready result, cannabis testing takes time. You may be held for several hours while the test is processed. If you refuse the test, most states will suspend your license automatically, even before any conviction.

Legal Limits for THC and How They Work

As of now, 17 states have set a legal limit for THC in the blood — usually 2, 3, or 5 nanograms per milliliter. These limits vary by state and are not based on strong science about impairment. A person who smokes cannabis regularly may have 5 nanograms in their blood while feeling completely sober, while an occasional user might be impaired at 2 nanograms. The limits exist because lawmakers needed a number, not because the number reliably predicts impairment.

In states without a set limit, the prosecution must prove you were impaired — they cannot rely on a number alone. This is harder to prove but still possible using field sobriety tests, officer observations, and informed testimony. Either way, the burden is on you to show you were not impaired, which is difficult once you have tested positive.

Some states use a "per se" law, meaning exceeding the limit is automatic guilt, like a 0.08 blood alcohol level. Others use an "impairment" standard, where the number is evidence but not proof. Know which standard applies in your state, because it changes how a case is built and defended.

Criminal Penalties for Driving High

A first conviction for driving high is usually charged as a misdemeanor and carries a license suspension of three months to one year, depending on the state. Fines range from $250 to $1,000. You may also be required to complete a drug education program or substance abuse treatment, which costs money and takes weeks or months.

Jail time for a first offense is less common but possible — some states impose up to 180 days. A second or third conviction within a set period (usually five to ten years) is treated more harshly: longer license suspension, higher fines, and mandatory jail time. A fourth conviction in some states is charged as a felony.

Beyond the when ready penalties, a conviction creates a permanent criminal record. This record shows up on background checks for employment, housing, professional licenses, and loans. Many employers, landlords, and licensing boards treat a drug-related driving conviction as seriously as a violent crime. The long-term cost to your life can far exceed the fines and jail time.

The Difference Between Legal Cannabis and Legal Driving

In states where cannabis is legal — Colorado, California, Washington, and others — the law is clear: you can buy it, possess it, and use it at home. You cannot drive after using it. The legality of the substance does not change the legality of driving impaired by it. This is the same as alcohol: you can buy and drink beer at home, but you cannot drive after drinking it.

Some people mistakenly believe that because cannabis is legal, driving high must also be legal, or that the penalties are lighter. This is false. The penalties are identical to those for alcohol impairment in most states. A conviction will show on your record as a drug-related driving offense, not straightforward as a traffic violation.

If you live in a state where cannabis is legal and you use it, plan ahead. Use it at home or at a friend's house where you will stay for several hours. Do not drive until you are certain the effects have worn off — this typically takes two to four hours for smoking and four to eight hours for edibles, though it varies by person and dose.

What Happens to Your License

A conviction for driving high triggers an automatic license suspension, separate from any jail time or fines. The length of suspension depends on whether it is your first offense and the laws of your state. A first suspension typically lasts three to twelve months. During this time, you cannot legally drive at all, even for work or medical appointments.

Some states offer a hardship or work license that allows you to drive to and from your job or school, but only after you have served part of the suspension. To get one, you must show the court that losing your license would cause severe hardship. The process requires paperwork and a court appearance.

After the suspension ends, you must pay a reinstatement fee (usually $100 to $500) and may be required to install an ignition interlock device in your car — a breathalyzer that prevents the engine from starting if it detects alcohol. Some states require this for all impaired driving convictions; others only for repeat offenders or high BAC levels. The device costs $50 to $100 per month to lease and maintain.

Refusing a Blood or Urine Test

You have the right to refuse a blood or urine test after a DUI arrest, but refusing carries its own penalties. Most states have "implied consent" laws: by driving on a public road, you implicitly agree to submit to a chemical test if arrested for impaired driving. Refusing the test triggers an automatic license suspension, usually longer than the suspension for a conviction itself.

A first refusal typically results in a one-year license suspension in many states, even if you are later found not guilty of driving high. A second refusal within ten years can result in a two-year suspension. The refusal is also admissible in court as evidence that you were trying to hide impairment, which can hurt your defense.

The choice to refuse is yours, but it is not a way to avoid consequences. Consult a lawyer before deciding. In some cases, refusing buys time for THC to leave your system before a test, but it also guarantees a suspension. In other cases, taking the test and fighting the result in court is the better strategy.

Frequently Asked Questions

How long after smoking or eating cannabis can I safely drive?

There is no universal answer because impairment varies by person, dose, and method. Smoking typically affects you within minutes and wears off in two to four hours. Edibles take longer to kick in (one to two hours) but last longer (four to eight hours or more). The safest approach is to wait at least four hours after any use before driving, and longer if you are uncertain about how it affects you.

Can I get a DUI for driving high if I have a medical cannabis card?

Yes. A medical cannabis card means you are legally allowed to possess and use cannabis for medical reasons, but it does not exempt you from impaired driving laws. You can still be arrested, convicted, and punished the same way as anyone else. The card may be relevant to sentencing or treatment requirements, but it does not prevent prosecution.

What if I smoked cannabis yesterday — can I still get a DUI today?

Possibly. If you are pulled over and show signs of impairment, you can be arrested and tested. A positive test does not prove you were impaired at the time of driving, since THC stays in your blood for days. However, if the officer observed impaired driving and you test positive, the prosecution may argue you were high while driving. This is why the legal limit exists — to make the case easier to prove.

Do I have to do a field sobriety test if a police officer asks?

You can refuse field sobriety tests (the walk-and-turn, one-leg stand, and eye test). Refusing does not trigger an automatic license suspension the way refusing a blood test does. However, your refusal can be used as evidence of impairment in court, and the officer can still arrest you based on other observations. Consult a lawyer about your state's laws before deciding whether to refuse.

What is the difference between a DUI and a DWI?

The terms vary by state. DUI usually means "driving under the influence" of any substance (alcohol, cannabis, or drugs). DWI usually means "driving while impaired" and is sometimes used interchangeably with DUI. Some states use both terms to mean different things — for example, DUI for lower BAC and DWI for higher BAC. Check your state's laws to know which charge you might face.