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Saliva Drug Tests Explained: How They Work and Why They’re Used

Written by Andrew Le, MD

UpdatedFebruary 29, 2024

Drug testing has become crucial in many industries, from hiring new employees to investigating accidents. Among the different types of drug tests, saliva tests have become popular as they are easy and effective.

Between 2015 and 2018, the percentage of workers testing positive for drugs rose in specific sectors. Wholesale trade saw a 20% increase, while retail and construction experienced increases of 14.9% and 13.2%, respectively.

In this guide, you’ll learn how saliva drug tests work, what substances they can detect, their accuracy, detection period, and how they compare to other drug tests. You’ll also touch on relevant laws.

Whether you're an employer looking for reliable drug testing solutions or just curious about the process, this article has got you covered.

What is a Saliva Drug Test?

A saliva drug test is a type of screening test used to detect the presence of drugs or alcohol in an individual's saliva. The test is non-invasive and painless, making it a popular choice for various testing scenarios. It is also known as a mouth swab or oral drug test.

Now, let's explore how this test actually works.

How Does a Mouth Swab Drug Test Work?

The process of conducting a mouth swab drug test can be broken down into the following steps:

  1. Use a collection stick with a sponge or absorbent pad on one end to swab the inside of the cheek or under the tongue to gather the saliva sample. Other methods like spitting, draining, or suction may also collect the saliva.
  2. The test can be performed on-site at a workplace, accident scene, dedicated laboratory, or specimen collection site.
  3. To ensure accurate results, individuals being tested are typically asked to refrain from eating or drinking anything for 10 minutes before the test. Food, beverages, medications, and mouthwash can interfere with the test's accuracy.
  4. After the sample is collected, it is analyzed for traces of controlled substances.
  5. The results can be obtained instantly on-site or sent to a lab for further analysis, depending on the testing method used.

What Substances Can a Saliva Drug Test Detect?

A saliva drug test can detect various substances, and the specific drugs depend on the type of test being used. Some tests are designed to detect a single substance, such as alcohol or marijuana, while others are multi-panel drug tests that can identify a combination of substances.

Did You Know?

Certain safety-critical professionals may require a 10-panel drug test, which checks for the misuse of prescription and illegal drugs. This test includes the US's five most commonly abused prescription drugs and five illegal substances doctors do not prescribe. Compared to the more prevalent 5-panel drug test that usually screens for five illicit drugs and sometimes alcohol, the 10-panel test is less common.

Common drugs of abuse that can be detected using a saliva drug test include:

  • Alcohol
  • Amphetamines
  • Barbiturates
  • Benzodiazepines
  • Cocaine
  • Marijuana (THC)
  • Methamphetamine
  • Opioids
  • Phencyclidine (PCP)

How Accurate Is a Mouth Swab Drug Test?

When conducted properly, mouth swab drug tests are highly accurate, with a precision rate of close to 98%. However, several factors can affect accuracy, including the

  • Type of test used
  • Specific drug being tested for
  • Concentration of the drug
  • Skill and expertise of the person administering the test
  • Quality of the testing device

The test timing within the drug's detection window can also impact accuracy.

Instant oral fluid testing kits and devices may not be as accurate as lab testing. Lab-based urine and blood tests are generally more accurate but more invasive and time-consuming.

How Far Back Can a Saliva Drug Test Detect Substances?

The detection window for a saliva drug test depends on various factors, including the test's sensitivity, the type of drug being tested, and the frequency of drug use. Generally, substances are detectable in oral fluid within 30 minutes of ingestion, making saliva tests highly effective for screening after an accident or in reasonable suspicion situations.

The general detection window in oral fluids is 5 to 48 hours, but this period can be longer for individuals who frequently use drugs or substances for an extended period.

How Long Do Saliva Drug Test Results Take?

The time required to obtain saliva drug test results varies based on whether the samples are sent to a lab or tested on-site. Lab results usually take around 24 hours to be processed, providing a more comprehensive sample analysis.

On the other hand, home drug testing kits and on-site testing devices, including those used for roadside tests, can provide results within minutes.

How does the Saliva Drug Test compare to other types of drug tests?

If you're considering getting saliva drug tests, it's crucial to understand how they compare to other available tests. Here's a simple table of the saliva drug test with other types:

Please refer to the discussion below for a more detailed explanation of the differences.

Saliva Swab Drug Test Vs. Blood Test

The saliva swab test offers a simple, painless, and non-invasive method for drug testing. On-site testing provides results within minutes, while lab testing takes about 2-3 days for results to be available.

On the other hand, the blood test is the most intrusive and may cause discomfort to the person being tested. It has a longer turnaround time, usually taking about one week for results.

In terms of cost, the saliva drug test is generally less expensive than a blood drug test.

The detection time is usually brief and rapid if the saliva test is conducted using an on-site testing kit. It can detect current drug use, but it may not detect previous drug use. Abstinence for a short period before the test can make it difficult to be detected.

Similarly, the blood test has a brief detection time and can reveal current drug usage, but it may not show historical drug use.

However, regarding accuracy, blood drug tests are considered more reliable, especially when the sample has yet to be manipulated.

Saliva Drug Test vs. Urine Test

While saliva drug tests are highly accurate when conducted correctly, urine tests are generally considered more accurate for detecting overall substance use.

A study comparing urine and saliva drug tests found that urine testing was more likely to detect overall substance use than oral testing.

Urine tests also have a longer detection window, making them a preferred choice for identifying an individual's historical drug use. However, saliva tests offer advantages such as being less invasive, faster, and more difficult to tamper with.

Saliva Drug Test vs. Hair Test

Both saliva and hair tests are non-invasive and offer their own set of advantages. Saliva tests are better at detecting recent drug use, typically within the past 5 to 48 hours, while hair tests can identify historical drug use for up to several months. Hair tests, however, require a longer turnaround time for results and are more costly than saliva tests.

How Long Do Drugs Stay in Saliva?

The detection period of drugs in saliva can vary depending on several factors, including the:

  • Specific drug used
  • Quantity of the drug consumed
  • Frequency of drug use
  • Duration of drug use
  • Method of drug administration
  • Individual's metabolism

For example, marijuana (THC) can be detected in saliva for up to 72 hours after use, while heroin may only be detectable for about an hour. Other substances, such as ecstasy and cocaine, can be detected for up to two days, while morphine may be detectable for up to three days. Methadone, on the other hand, can be detected for up to 10 days.

How to Get a Saliva Drug Test?

There are three main ways to obtain a saliva drug test:

  • Instant Oral Fluid Testing Kits: These kits allow immediate on-site testing, providing results within minutes. They are easy to use and cost-effective.
  • Instant Oral Fluid Testing Devices: Similar to testing kits, these devices offer quick results on-site.
  • Lab Testing: If a more comprehensive analysis or confirmation testing is necessary, samples can be sent to a laboratory for further examination.


If you want to get tested and pass a saliva drug test after smoking weed, focus on the short detection window (around 12-24 hours). Drink water, mouthwash, or rinse with low-concentration hydrogen peroxide to reduce detection time further. Avoid ineffective methods like sucking on a penny. Check out this video for more tips on passing the test: How to pass a Saliva Test for TCH

What are the Saliva Drug Test Laws and Compliance?

Employment drug screenings are regulated at both the federal and state levels, and it is crucial to be aware of the relevant laws and regulations to ensure compliance. Some key laws related to saliva drug testing include:

  • Title VII of the Civil Rights Act of 1964: Prohibits employer discrimination based on race, color, religion, sex, or national origin. Drug testing must be administered fairly and consistently to comply with this law.
  • The Fair Credit Reporting Act (FCRA): Applies when an employer uses a third-party screener to perform a drug test. Employers must provide background check disclosure and authorization forms before conducting the test.
  • State Laws: State laws vary, and some have specific limitations on pre-employment drug testing and the substances that can be tested.

The Bottom-line

Saliva drug tests have become valuable in various settings, including workplaces, law enforcement, and healthcare facilities. Their non-invasive nature, fast results, and accurate detection of recent drug use make them a popular choice for immediate screening.

While saliva drug tests offer many benefits, it is essential to choose the appropriate testing method based on the specific requirements of each situation. Employers and individuals must also stay updated on the relevant laws and regulations to ensure a fair and compliant drug testing process.

As drug testing technology advances, saliva drug tests are likely to play a significant role in maintaining safe and drug-free environments, ultimately promoting the health and well-being of individuals and organizations alike.

Employers and individuals can effectively address substance use and create safer communities by staying informed and making informed decisions.

FAQs on Saliva Drug Tests:

What can a saliva test detect?

Saliva testing can be used to check for various conditions and diseases, such as Cushing's disease, anovulation, HIV, cancer, parasites, hypogonadism, and allergies.

What's the most common false positive drug test?

The most commonly reported false-positive drugs are amphetamine and methamphetamine.

How to fix a false positive drug test?

You can ask for another test if you get a false positive result. Many places will be understanding and allow you to retake the test. Providing evidence, like a letter from a doctor or pharmacist about a prescription medication, can be helpful.

What causes a drug test to be canceled?

A drug test can be canceled if the testing process has a serious flaw. It's neither a positive nor a negative result, and employers can't use it as a basis for taking action against an employee.

What can cause a negative drug test?

Potentially inappropriate negative drug test results can be caused by limited assay specificity, absence of the drug in the urine, presence of the drug in the urine but below the established cutoff, specimen manipulation, and laboratory error.

What foods should you avoid before a drug test?

Before a drug test, avoid seafood for 48 hours, alcohol, coffee, tea, tobacco, strenuous exercise for 24 hours, and certain foods like avocados, bananas, eggplant, pineapples, plums, tomatoes, or walnuts for 48 hours.

How long does a saliva test detect smoking?

A saliva test can detect cotinine from smoking for up to 4 days, making it a sensitive method. For long-term use, hair testing is more reliable, detecting tobacco products accurately for 1 to 3 months after quitting.

Can a drug test go wrong?

Drug screenings can be scary, and false-positive results can happen, even if you've done nothing wrong. Many prescription medications, over-the-counter drugs, supplements, and certain foods can lead to false positives.

What can I drink to detox from smoking?

Drinking plenty of water, around 8 to 10 glasses a day, can help detoxify your body by flushing out toxins and improving your overall health and skin quality.