Drug-Impaired Driving and THC Limits in Canada

The short answer

Driving while impaired by any drug is a crime in Canada. That includes cannabis, illegal drugs and prescription medication. There are two ways to be charged: being impaired, or having a drug level in your blood at or above a legal limit within two hours of driving. Drug-impaired driving cases often depend on technical evidence that deserves careful review.

Two ways to be charged

• Impairment: Your ability to drive was impaired to any degree by a drug, or by a drug and alcohol together. No set level is needed.
• Blood drug concentration: Your blood drug level was at or above the legal limit within two hours of driving. No proof of impairment is needed.

The legal drug limits

Lower THC offence (summary only)

• Level: 2 ng to less than 5 ng of THC per mL of blood.
• Penalty: A maximum fine of $1,000 (s. 320.14(4)).

Main offence (hybrid)

• THC: 5 ng or more per mL of blood.
• THC with alcohol: 2.5 ng of THC per mL plus 50 mg of alcohol per 100 mL of blood.
• GHB: 5 mg per litre of blood.
• Other drugs: Any detectable amount of cocaine, methamphetamine, LSD, ketamine, PCP, psilocybin, psilocin or 6-MAM.

The main offence carries the same penalties as alcohol-impaired driving, including a $1,000 minimum fine for a first offence.

How police test for drugs

• Roadside oral fluid test: If police reasonably suspect drugs, they can demand a saliva sample on an approved device (s. 320.27(1)(c)).
• Field sobriety tests: Police can demand physical coordination tests at the roadside.
• Drug recognition evaluation: A trained officer assesses you at the station, checking things like your pupils, pulse and balance.
• Blood sample: Police can demand blood to measure drug levels.

In Ontario, a poor drug recognition evaluation leads to a 90-day roadside suspension and a 7-day impoundment.

Prescription and medical cannabis

A prescription is not a defence if the drug impaired your driving. The concentration offence can also apply to medical cannabis users, even if they felt completely fine.

THC can stay in the blood of regular users for a long time. For example, someone who uses medical cannabis daily may be over 2 ng/mL many hours after their last use, without feeling any effect.

The evidence in a typical case

Drug-impaired driving cases often rely on the officer's observations of your driving and behaviour, the roadside oral fluid result, the drug recognition evaluation report, and a toxicology report from a blood sample. Each of these has its own rules. For example, a positive saliva test only gives police grounds to investigate further, and the drug recognition evaluation must follow a set series of steps.

What happens after you are charged

1. Roadside penalties: In Ontario, a poor drug recognition evaluation leads to a 90-day suspension and a 7-day impoundment.
2. Disclosure: The Crown provides the evaluation report, the toxicology results and any video.
3. Defence review: Your lawyer reviews whether each test was lawful and done properly.
4. Resolution or trial: The case either resolves or goes to trial.

Possible defences

• The demand: Police may not have had reasonable suspicion for the roadside test, or grounds for the station demand.
• Charter rights: Police may not have told you of your right to a lawyer, or given you a real chance to use it.
• The evaluation: The drug recognition evaluation may not have been done or recorded properly.
• Timing: The blood sample may not have been taken within two hours of driving.
• Other explanations: Signs like red eyes or slow reactions may have other causes, such as fatigue or a medical condition.

See impaired driving defences in Ontario.

Effects beyond the sentence

A conviction for the main drug-impaired offence is a criminal record, with the same insurance, employment and travel consequences as an alcohol-impaired conviction. Because the maximum is 10 years by indictment, it can also make a permanent resident inadmissible for serious criminality.

Mixing alcohol and drugs

When alcohol and cannabis are combined, the law sets a lower threshold for THC. A driver with 2.5 ng of THC per mL of blood and 50 mg of alcohol per 100 mL of blood commits the main offence, even though each level on its own would be below the usual limit. Combining substances can also increase impairment more than either would alone.

Possible outcomes

What to do now

• Gather records of any prescriptions or medical conditions that could explain your symptoms.
• Write down when you last used cannabis or any medication, and how much.
• Do not drive until your suspension has ended and your release papers allow it.

Medical conditions and other explanations

Many signs that officers associate with drug use can have other causes. Fatigue, allergies, diabetes, eye conditions, anxiety and some neurological conditions can affect pupils, balance or coordination. If you have a condition like this, medical records and a letter from your doctor can help explain your symptoms and challenge the evidence of impairment.

Drug testing at a collision

After a collision, police may take a closer look at drug use. They still need a lawful basis for each demand. If a blood sample was taken at a hospital, how it was obtained can be an issue.

How we can help

We can review the drug evaluation, the blood results and the police video, and test whether the evidence supports the charge. Call (647) 223-1980 for a free consultation.

Frequently asked questions