How long does THC stay in saliva?

Since the early days of drug testing, urine has been the preferred testing matrix. Now, saliva is emerging as a viable alternative, especially for drug treatment, workplace programs, legal settings, and driving under the influence of drugs (DUID). Read on to find out how long weed stays in your system (and salivary glands), how a mouth swab drug test differs from a urinalysis, a mouth swab drug test weed timeline, and much more.

What is a mouth swab drug test?

A mouth swab drug test screens for substance abuse. Also called a saliva drug test or oral fluid testing, saliva drug testing is a favorite of authorities because it is brief, lasts two to three minutes, is non-invasive, and gives instant answers. Additionally, the specimens are impossible to tamper with.


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  • This specifically prepared mouthwash allows you to get rid of any detectable drug toxins that may have remained in your mouth moments before the drug test.
  • The 1-ounce bottle makes it simple to dispose of or conceal in the moments leading up to the test.

The substances a mouth swab can detect vary depending on the type of test. The difference usually lies in the number of drugs being tested. Multi-panel drug screens such as 5-panel, 9-panel, and 10-panel usually check for the following substances alone or in combination:

  • Alcohol
  • Amphetamines
  • Benzodiazepines
  • Barbiturates
  • Cocaine
  • Marijuana/THC
  • Opioids
  • Propoxyphene
  • Methadone
  • Methaqualone
  • Phencyclidine/PCP

How long does weed stay in your system?

Studies suggest that weed can be found in the body for up to 1–30 days in bodily fluids and up to 90 days in hair. More about what is the detox time frame of cannabis. However, there isn’t a definitive answer to how long does weed last in your system. Experts say it all comes down to individual variables, such as:

  1. Dosage and frequency of use. The more marijuana you consume, the longer your body takes to break it down and excrete it in urine. According to April Hatch, RN, the co-founder of Cannabis Care Team, “how much you consume and how often will influence how long cannabis stays in your system, but it can depend on an individual’s metabolism as well.”
  2. Genes: Cytochrome p450 polymorphisms play a key role in accelerating THC metabolism.
  3. Body fat percentage: THC-COOH is lipophilic, which means it remains longer in the fat cells. If your BMI is high, your body will retain more THC and your detection rate will be more than a slim person.
  4. Metabolism: How fast or slow your metabolism is can also determine how long weed will stay in your system.

When you smoke, vape, or otherwise use cannabis in food and drinks, THC is broken down into at least 80 different byproducts, which then quickly make their way to your fat cells, the brain, and other organs. These byproducts are gradually eliminated through feces and urine.

Weed hits everyone differently. The “dopey” feeling usually lingers for up to 6-8 hours and often depends on the quality of the cannabis being used and the amount of THC in it.

Weed usage can be divided into three:

  • Infrequent usage – less than twice a week
  • Moderate usage – several times a week
  • Chronic usage – daily

What about cannabis edibles? How long do edibles last?

Cannabis-infused ‘pot gummies’ and ‘happy brownies’ are smokeless alternatives containing either or both THC and CBD. While you might feel high within minutes after smoking, edibles take 30–90 minutes to set in. With higher doses, you may feel the effect within 15–20 minutes. The edible high can last for 4-6 hours, with the peak effect occurring about 2-3 hours after consumption.

Saliva tests can show traces of THC use for up to 3 days, although this number may be different if you ingest CBD gummies, which usually contain ≤ 0.3% THC.

Mouth Swab Drug Test For Marijuana

How long does THC stay in saliva glands?

Most research shows that THC remains in the saliva for up to 24 hours with a cut-off limit of 0.5 ng/mL. A 2020 study in Clinical Chemistry showed that THC can be detected in the oral fluid of frequent cannabis users 72 hours after the last consumption.  For chronic heavy users, saliva drug test THC detection times could be much longer – up to 30 days.

According to a 2019 study, when given 125mg of vaporized THC, most participants (with a history of moderate use) tested negative three hours after use.

Weed can enter the body fluids through both active and passive exposure. However, you will end up with THC in your saliva only if you have smoked, vaped, or ingested cannabis.

What if your mouth has been washed, or if you have eaten or drunk since the last use? Well, in that case, the drug test results may well be negative if you are an occasional smoker. Also, if THC is removed from your oral cavity or reduced below the cut-off limit, then the result will show negative. Simply put, the longer you go after smoking, the fewer THC metabolites are left to detect.

How does a mouth swab drug test work?

A common misconception is that the saliva tests simply collect remnants of weed that have been ingested or smoked. In reality, it collects byproducts of drug detoxification. The body breaks down the weed and releases metabolites into circulation, which then move as waste to oral fluids in the same way that they move to feces and urine.

Urinalysis and swab drug tests look for entirely different compounds. A urine drug test screens for THC-COOH, the major metabolite of THC. Saliva drug tests, on the other hand, look for delta-9 THC, the activated form. That means simply brushing your teeth and rinsing your mouth with water or non-alcoholic mouthwash before a test won’t simply remove evidence of weed, especially if you are a chronic user.

Are mouth swab drug tests accurate?

Accuracy varies between rapid kits, oral fluid testing devices, and lab testing. Typically, rapid oral drug testing kits and devices aren’t as accurate as lab testing. A 2017 study reported 97.5% accuracy for a portable saliva drug test compared to lab-tested samples. The method of sample collection, the substance tested for and its concentration, and whether or not salivary flow was altered can also affect the accuracy of the test.

How to pass saliva drug test for THC?

Let’s get real: the best way to pass a mouth swab drug test for weed, or any drug test for that matter, is abstinence. Abstinence for 24–48 hours will naturally clear THC from the saliva. Also, do not eat, drink, or take prescription drugs at least 30 minutes before your test. This is important because anything you’ve recently consumed can trigger a false-positive result (more on that below!).

What to do when you get pulled over or have only a few hours’ notice? You may try your luck with oral fluid adulteration methods – citric acid candy or chewing gum – that stimulate the production of saliva and inevitably change the pH and concentration of active drug compounds in the saliva. However, it is not without limitations. Saliva equilibrates every 10 minutes, which is why nothing is allowed in your mouth for 10 minutes to rule out sample contamination.

What are the other methods to test marijuana?

Besides mouth swab drug tests, there are a variety of drug tests that authorities can request. The popular ones include:

  1. Urine Drug Test. Urine is the most popular specimen of choice for drug testing. Urine samples contain ample amounts of the drug therefore, its byproducts can easily be detected. There are two types of urine drug tests: immunoassay and gas chromatography/mass spectrometry (GC/MS). If the first test i.e., Immunoassay, comes back positive, GC/MS is done as a confirmatory test.
  2. Blood drug test. Blood drug test better indicate recent substance abuse. The metabolite-to-drug ratio in the blood is used as an indication of chronic versus occasional marijuana use. Blood drug test is often conducted as a post-crash protocol if there’s evidence that the accident involved illicit drugs or alcohol.
  3. Hair follicle test. Hair follicle drug tests not only detect drugs that remain in your follicles for up to 90 days but also the pattern of use. After being smoked or consumed, cannabinoids make their way to hair follicles and sweat glands on the scalp via small blood vessels. Hair tends to grow about 0.5 inches per month. That means, if you test 100mg of 1.5-inch hair strands, they will provide signs of drug use during the past three months.

Can drug tests lead to a false positive?

A worry for anyone, especially those who have not taken any drugs and are undergoing a drug screen – be it a blood, urine, hair, or saliva test – is false positives. Though drug screening methods have improved over the years, false positives are still very possible.

But how does this happen? Sometimes it can be the result of a laboratory error. But more often, false positives are due to medications like antidepressants (Venlafaxine and desvenlafaxine), decongestants (pseudoephedrine), sleep aid drugs, NSAIDs (ibuprofen and naproxen), proton pump inhibitors such as pantoprazole, antibiotics (levofloxacin and ofloxacin), and some prescription medications.

If you think your mouth swab test results are inaccurate, talk to your physician or employer to reconfirm the results with a gas chromatography test.

Takeaway on how long does THC stay in saliva

Cannabis doesn’t stay in saliva for long. Mouth swab drug tests are designed to tell if you were on cannabis recently. If you have a day or two before the swab at work, stop using weed immediately.