Medically Reviewed by
Jason Crawford

Article Last Updated on January 8, 2023

Drug testing is becoming even more common in today’s modern world as new drug tests with bigger detection windows appear. Whether it’s mandatory pre-employment testing or regular workplace drug testing, your company may have strict drug screening regulations in place and you’ll need to comply with them. 

Maybe you’re a parent who wants to check your kid for drug use, and you decide to do a drug test at home. No matter what the reason may be, drug testing is here to stay, as more drug test kits are bought over-the-counter in preparation for mandatory drug tests at work.

The screening test checks for the presence of the most common drugs like:

  • Barbiturates;
  • Benzodiazepines;
  • Amphetamines;
  • Methamphetamines;
  • Opiates;
  • Opioids;
  • Codeine;
  • phencyclidine (PCP);
  • Methadone;
  • Oxycodone;
  • Cannabis.

But as cannabis is the most abused drug around the world, the most common drug screenings are for cannabis. Even though Cannabidiol (CBD) may not show up on a drug test,  testing for cannabis is done by measuring the levels of Tetrahydrocannabinol (THC) or THC metabolites (THC-COOH). In this article we’ll focus on the oral fluid drug test and what the detection window is when detecting weed.

Drug Detection Window            

Depending on the period of time that has passed before you last consumed cannabis, the drug detection period is the time during which a drug can be detected in a biological sample. The biological samples that get tested have different detection times and a cutoff level is set to optimize drug detection and minimize false positives. The biological staples that are tested are blood samples, urine samples, oral fluids, breath, or hair samples.

What Influences Drug Testing Results

The negative or positive result on your drug screen can depend on some variable factors like:

  • The amount of cannabis that’s consumed;
  • The frequency of use;
  • The hydration levels;
  • The tolerance level;
  • Physical activity, metabolic rate, and BMI (because THC binds to fat cells in the body);
  • Other conditions users might have.

Types of THC Drug Tests

Depending on the testing method, there are a few general drug tests:

  • Urine drug tests. Urine testing is done by collecting a urine sample and testing it for the presence of THC.          
  • Blood tests. Blood testing is done by collecting a blood sample and testing it for the presence of THC.
  • Saliva drug tests. Saliva testing is done by taking a sample of the oral fluid and testing it for the presence of THC.
  • Hair follicle tests. The hair test is done by taking a hair sample and testing it for the presence of THC.
  • Breath tests. The breathalyzer is a new method of drug testing that can measure the amount of tetrahydrocannabinol (THC) in the user’s breath by breathing into it.

How Is the Mouth Swab Drug Test Done?

Oral fluid testing is one of the least invasive forms of drug testing that’s done by testing a swab of saliva and comparing it with the cut-off (quantitative threshold set for the test by the Substance Abuse and Mental Health Services Administration – SAMHSA). 

To test for drugs found in saliva, the mouth swabs are screened with the enzyme immunoassay technology and samples that test positive are further tested with more specific testing methods like liquid chromatography and mass spectrometry to confirm findings.

This is a newer type of drug testing that is more expensive than urinalysis and blood testing. Marijuana use can show on saliva drug test results when the methods of consumption are ingestion or smoking.

Saliva Testing and Detection Times

According to a study done in 2014 by the National Institutes of Health in Baltimore, the detection time of cannabinoids in oral fluid depends mostly on how often weed is consumed. In recent years oral fluid may be used for roadside testing in countries where weed is legal and there are laws that enable testing for weed.

And how long does THC stay in saliva, you’re wondering? Well, here’s your answer:

  • For occasional users, the time for detection is 1 to 3 days. Occasional users are considered people that consume cannabis less than 3 times a week.
  • For chronic users, the time of detection is 1 to 29 days. Chronic users are people that consume cannabis at least once a day.

Passing a Saliva Test?

Since saliva tests rely on finding THC and THC metabolites in the lining of the mouth, it’s easier to pass them on shorter notice compared to urine testing.

A few things you can do in order to pass your test include brushing your teeth more times in the hours leading to a saliva test and using mouthwash to clean your mouth. Focus on your gums and tongue by scraping them with a tongue scraper, and also floss.

You should also consume a lot of water and make sure you rinse your mouth thoroughly before your test.  Moreover, you should try eating fatty foods since THC is fat-soluble, and eating those foods can boost the absorption rate of THC. Since saliva tests look for THC, you shouldn’t have a problem with the THC-COOH levels increasing in your system.

Final Thoughts on Oral Drug Testing

As marijuana legislation is striving towards more rigorous testing in the workplace and especially for drivers who are suspected of marijuana use on the road, drug tests are becoming extremely accurate. If the goal is to determine the recent use of weed, the breath test (or using the breathalyzer) would be the best option. 

Although, workplace drug testing generally focuses on urinalysis, and in some cases, mouth swab drug tests. These tests are performed by collecting a saliva sample from the person being tested and the sample is later screened with the enzyme immunoassay technology. Samples that test positive are sent for further analysis by using liquid chromatography and mass spectrometry to confirm findings.

Depending on how often you consume weed, the detection time for saliva testing varies. For occasional users, the time of detection can vary from 1 to 3 days, and for chronic users, the detection time can be from 1 to 29 days. 

If you have a mandatory workplace drug test scheduled in the near future, abstaining from using weed in the weeks leading up to the test would surely help. However, please note that we are not encouraging cheating on drug tests. This article is purely for educational purposes only.

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.