Medically Reviewed by
Jason Crawford

Article Last Updated on December 30, 2022

Due to marijuana’s popularity and the fact that it’s consumed all over the world, lawmakers came up with multiple ways to measure how this controlled substance impairs drivers and people who operate heavy machinery. So, cannabis drug testing became a regular practice. But many are still wondering: can you drive high and can a breathalyzer detect marijuana?

Cannabis consumption can be detected by testing human hair, saliva, blood, urine, and since very recently, yes, testing the breath by using a breathalyzer device. Authorities all over the world are focusing on finding effective ways to measure how cannabis affects drivers. This is particularly popular in the US where the National Highway Traffic Safety Administration together with Congress are trying to find an effective way to measure how much weed impacts drivers.

While there’s still no standard measure that determines tetrahydrocannabinol (THC) impairment, the breathalyzer may become the gold standard for drug testing in the future. To find out all you need about the breathalyzer and marijuana DUI’s, read on.

The 411 on Cannabis Breathalyzer

Because both medical marijuana and recreational marijuana are legal in a lot of US states, law enforcement has a problem with an increasing amount of stoned drivers. Driving under the influence of weed is never a good idea since it affects your driving abilities. For that reason, a lot of companies are focusing on creating a cannabis breathalyzer. 

This device can detect THC on the spot and give police officers a quick result on whether or not the driver is under the influence of cannabis. To be on the safe side while driving, cannabis users need to wait until the psychoactive effects of THC pass before getting in the car.

Can an Ignition Interlock Device Detect Marijuana?

A DUI conviction means that you need to install an ignition interlock device (IID) in your vehicle, which is a breathalyzer that detects the presence of alcohol. The IID is intended to prevent drunk driving after you’ve been convicted of a DUI. Once you get into the car and breathe on the IID, the car won’t start if the breath test shows you’ve been drinking. 

Some cannabis users are wondering whether a car breathalyzer can detect marijuana, and the answer is no. The IIDs that are available on the market today only detect alcohol in the system. Still, even though they don’t detect weed, that doesn’t mean that you should operate your vehicle while under the influence of cannabis, even if cannabis is legal for recreational use where you live.

Recreational Use of Cannabis and DUIs vs Medical Use of Cannabis and DUIs

Getting behind the wheel requires you to drive responsibly for your sake and for the sake of every person in traffic.  As we’ve previously mentioned, DUIs aren’t only related to alcohol. You can get a DUI if you’ve consumed any substance that affects your driving, and that includes drugged driving.

If an officer suspects you’ve been consuming alcohol or illegal substances, they may pull you over and subject you to a blood or urine test to check for drugs. While state laws may vary, if you’re found with drugs in your system, you could be held accountable under the law. Common penalties for DUIs include:

  • A suspended driver’s license;
  • A fine;
  • Jail time;
  • A controlled substances charge;
  • An impounded vehicle;
  • Being submitted to a random drug test;
  • Mandatory enrollment in a drug treatment program.

Keep in mind that a medical marijuana prescription won’t exempt you from a DUI. If you’re stopped by local law enforcement and you’re under the influence of cannabis, it won’t matter that you have a prescription since you’re breaking the law – therefore, you will be sanctioned.

How Far Are We From Getting a Marijuana Breathalyzer on the Market?

Nowadays, roadside drug testing is done through a person’s saliva which detects if you’ve consumed cannabis in the past few hours. Since there’s no general cannabis intoxication threshold, every state has their own unique laws. For example, the California Highway patrol has a marijuana test that has a 95% accuracy rate. The test has a plastic swab stick that’s stuck to a computerized unit and it’s used for roadside drug testing. However, this isn’t the same as a breathalyzer test, although some companies are getting closer to that goal.

An Oakland-based diagnostics company, Hound Labs, is focused on producing a marijuana breathalyzer. The founder, Mike Lynn, stated that clinical trials started in 2016 and the company is getting close to finishing the product. Their breathalyzer consists of a small plastic cartridge with a tube sticking out at the end intended for blowing into it. After blowing, the screen indicates whether you’ve consumed weed in the past 2 hours. Their device also doubles as an alcohol breathalyzer so it gives law enforcement a two-in-one device.

The Hound Labs Breathalyzer

2019 was a significant year for Hound Labs, since it was the year during which they had their clinical trial regarding their new product – Hound Breathalyzer. It was conducted at the University of California San Francisco and was as extensive as a study involving breathalyzers can be. The study concluded that their breathalyzer showed the presence of THC if users consumed cannabis in the past 2-3 hours. 

According to the trial results, the cannabinoid THC moves from the blood to the breath rather quickly and it can be detected in the breath even up to three hours. Mike Lynn claimed that the test was extremely sensitive, so it didn’t matter whether you took a small puff of joint or ate a few edibles, the test would show a positive result because it measures the THC in picograms.

Other Scientific Breakthroughs

Research by UCLA chemists found its way in Organic Letters in 2020, giving an overview of a chemical discovery that aids to create an electronic breathalyzer. The scientists applied a similar oxidation process which is applied in alcohol breathalyzers. The device removes the hydrogen molecules from THC which enables the test to detect the presence of THC. The scientists aim to achieve the same results as they do with other drug screens but much faster, however, a breathalyzer device isn’t likely to be available in the near future.

The researchers at the University of Pittsburgh have also been researching a new breathalyzer that can detect the amount of THC in the breath. Their findings are presented in Science Daily and the review goes over how the breathalyzer is made. This device uses carbon nanotubes which are 100,000 times smaller than human hair and can detect THC levels similar to the gold standard of the mass spectrometry test. The professors, Alexander Star and Ervin Sejdic, used carbon nanotubes and machine learning to separate and detect the THC molecules in the breath.

The Problems with Marijuana Roadside Testing

When it comes to drunk driving laws, there is an official guideline for Blood Alcohol Concentration – anything at or over 0.08 guarantees you’ll get a DUI. However, roadside cannabis testing isn’t possible at the moment, so police officers assume consumption based on the behavior of the driver, including saliva and blood tests. 

Some states believe that the threshold for THC levels in the blood should be 5ng/ml, although the limits are arbitrary, and weed can’t be viewed the same as alcohol. Since alcohol is water-soluble, it diffuses through the body rather quickly, so the effects of impairment are mostly felt one hour after consumption, which makes the alcohol breathalyzer an ideal tool for police officers to measure for driver impairment.

Marijuana, on the other hand, ends up in our fatty tissues and the maximum THC levels occur within 10 minutes of smoking. Detoxing is a whole other procedure since every user takes a different time to detox from weed depending on their metabolism, personal tolerance level, how much weed they’ve consumed, and other conditions. Therefore, it’s possible to fail an impairment test even if you haven’t used weed that day.

Final Thoughts on the Marijuana Breathalyzer

As weed is becoming legal in a lot of US states, the risk for cannabis DUIs increases exponentially. Hence, it would be useful if police officers had the aid of specialized marijuana breathalyzers for roadside detecting.

In theory, the marijuana breathalyzer would solve this problem as it would be able to detect THC levels immediately. The only problem is that there’s no uniform impairment level for cannabis, so in order to be able to implement breathalyzers as a standard procedure, that would have to change. More and more researchers are focusing on developing this type of technology, so we can probably expect cannabis breathalyzers to become a standard in the future.

A passionate advocate for the benefits of cannabis. Fraser Horton, who has a background in botany and a strong love of nature, has spent years researching how cannabis affects the body and mind. He established Leaf Nation in 2020, where he has devoted himself to educating people about the legalisation of marijuana and its safe and responsible use. Fraser is committed to highlighting cannabis’ potential for improving wellness and working to dispel the stigma associated with its use.


The information presented on this page is provided as a public service to aid in education and is derived from sources believed to be reliable. Readers are responsible for making their own assessment of the topics discussed here. In no event shall Leaf Nation be held reliable for any injury, loss or damage that could happen if using or abusing drugs.