What is the THC DUI limit in Illinois?

Illinois has a per se THC limit of 5 ng/mL in whole blood and 10 ng/mL in other bodily substances (saliva, urine). The sample must be collected within 2 hours of driving. Exceeding these limits is treated as proof of impairment regardless of actual driving behavior. Medical cannabis patients are exempt from the per se presumption but can still be charged for actual impairment.

Can you get a DUI for weed in Illinois?

Yes. A first cannabis DUI is a Class A misdemeanor carrying up to 1 year in jail, up to $2,500 fine, and 1-year license revocation. A third offense escalates to a Class 2 felony (3-7 years prison, $25,000 fine, 10-year license revocation). DUI causing death is a Class 2 felony with 3-14 years prison. THC can remain above 5 ng/mL in blood for 24+ hours after heavy use.

Can police search your car for smelling cannabis in Illinois?

Currently yes — the odor of cannabis can still be used as probable cause for a vehicle search in Illinois. SB 0042, which would prohibit using cannabis odor alone as probable cause, passed the Senate 33-20 but has stalled in the House. Until the bill passes, officers may use cannabis smell to justify searching a vehicle even though possession is legal.

Illinois Cannabis DUI — 5 ng/mL Per Se Limit

Legal Disclaimer: This information reflects Illinois cannabis law as of April 2026 and is for educational purposes only. It is not legal advice. Laws and regulations change — always verify current rules with the Illinois Department of Financial and Professional Regulation or a qualified attorney. Cannabis remains illegal under federal law.

Last verified: March 2026

The Per Se THC Limits

Illinois uses a per se standard for cannabis DUI, meaning that exceeding the blood THC limit is treated as proof of impairment — no additional evidence of impaired driving is required:

Test Type	Per Se Limit	Notes
Whole blood	5 ng/mL THC	Delta-9 THC (active compound)
Other bodily substance (saliva, urine)	10 ng/mL THC	Higher threshold for non-blood tests
Testing window	Within 2 hours of driving	Blood or other sample must be collected within this window

The 2-hour testing window is critical. If law enforcement cannot collect a blood or bodily fluid sample within 2 hours of the stop, the per se presumption may not apply. However, officers can still charge DUI based on observed impairment, field sobriety tests, and Drug Recognition Expert (DRE) evaluations.

Regular Users at Risk

THC can remain in blood above 5 ng/mL for 24+ hours after heavy use. A daily consumer may be over the per se limit even after sleeping a full night. This is not a "don't smoke and drive" issue — it is a pharmacological reality that the per se standard does not account for.

Medical Patient Exemption

Registered medical cannabis patients receive a partial exemption from the per se standard:

Medical patients cannot be charged solely for exceeding the 5 ng/mL blood THC threshold
Medical patients CAN be charged for actual impairment based on driving behavior, field sobriety tests, and DRE evaluations
The exemption does not protect medical patients who are actually impaired — it only removes the per se presumption

This is a meaningful distinction. Without the per se presumption, prosecutors must prove actual impairment through other evidence, which is a higher bar. But medical patients are not immune from DUI charges — impaired driving is still illegal regardless of your medical status.

Penalty Escalation

Offense	Classification	Penalties
First offense	Class A misdemeanor	Up to 1 year jail, up to $2,500 fine, 1-year license revocation
Second offense	Class A misdemeanor (mandatory minimum)	Mandatory 5 days jail OR 240 hours community service, up to 1 year jail, up to $2,500, minimum 5-year license revocation
Third offense	Class 2 felony	3–7 years prison, up to $25,000 fine, 10-year license revocation
Fourth+ offense	Class 2 felony	3–7 years prison, up to $25,000 fine, permanent license revocation
DUI with injury	Aggravated DUI (Class 4 felony+)	1–12 years prison depending on severity
DUI causing death	Aggravated DUI (Class 2 felony)	3–14 years prison, mandatory consecutive sentences

SB 0042: The Odor Bill

Senate Bill 0042, the cannabis odor bill, passed the Illinois Senate 33–20 but has stalled in the House. The bill would:

Prohibit law enforcement from using the odor of cannabis alone as probable cause for a vehicle search
Require additional evidence of impairment or criminal activity beyond smell
Address concerns that cannabis odor is used as a pretext for discriminatory traffic stops

Under current law (without SB 0042), the smell of cannabis in a vehicle can still constitute probable cause for a search. Officers may use odor as justification to search a vehicle, even though cannabis possession is legal.

Transport Requirements

Cannabis must be transported in vehicles in a specific manner:

Sealed container: In a sealed, odor-proof, child-resistant container
Original packaging: Keeping cannabis in its original dispensary packaging is the safest approach
Not accessible: Best practice is to store cannabis in the trunk or a locked glove compartment
No consumption: Neither the driver nor any passenger may consume cannabis in a vehicle

Implied Consent

Illinois operates under an implied consent law. By driving on Illinois roads, you have implicitly consented to chemical testing if an officer has reasonable grounds to believe you are impaired. Refusing a blood or breath test triggers:

First refusal: 12-month statutory summary suspension of driving privileges
Second refusal: 36-month statutory summary suspension

Cannabis DUI Laws in Illinois