Medically Reviewed by
Jason Crawford

Article Last Updated on January 17, 2023

Drug screening has become the new norm in countries all around the world as a result of legalization laws and an increase in substance abuse. Some workplaces have mandatory pre-employment testing for their applicants, and even regular monthly testing for their employees.

Pre-employment drug testing is very common in the United States, and the top 5 industries that require testing are government, healthcare, manufacturing, automotive, and transportation and logistics. Companies test for drugs like barbiturates, methamphetamines, amphetamines, opiates, methadone, oxycodone, PCP, as well as for cannabis. But the USA is not the only country that does this – other countries around the world are picking up on these drug screening regulations in their companies by the day.

Depending on the type of drug you use, and the type of test you do, the window for detection and detox varies. Nowadays, you can even buy over-the-counter drug test kits that are FDA-approved at CVS and Walgreens. Yes, you heard that right… You can buy an at home drug test at CVS or Walgreens. Depending on whether you have a mandatory drug testing at work, or you want to check your kids for drug use, you can now do that from the comfort of your own home. Home drug testing kits are used more and more each day, and below you can find all the info you need about these test kits.

Types of THC Drug Tests

Different types of drug tests can determine the concentration of THC metabolites (THC-COOH)  in your body. Because THC binds to the fat cells in the body, the detection of weed can even depend on your body mass index. When testing for drugs, the most commonly used tests are:

  • Urine test;
  • Blood test;
  • Mouth swab (saliva) test;
  • Hair test;
  • Home test.

Urine Drug Test

The most common type of drug testing is urinalysis. This is a painless procedure that is done by taking a urine sample which is tested for the presence of illegal drugs in the body.

After the sample has been examined, it’s later compared to the federal cut-off levels for the type of drug that the technicians are searching for. Depending on how often you use cannabis, the detection time is different. If you’re a nonuser, after using weed once, there’s a 72-hour period for detecting THC metabolites.

Blood Drug Test

This type of test is done by drawing blood and testing it for the presence of drugs and opiates. As a result of the kidneys filtering the blood numerous times during one day, the window for drug testing via blood is the shortest.

The detection time varies depending on whether users consume cannabis frequently or they are occasional users. For occasional users, the test will yield a positive result from 4 to 24 hours after the use of cannabis. For frequent users, however, this can even be one week.

Mouth Swab Drug Test

This is one of the least invasive forms of drug testing. Oral fluid testing is done by testing a swab of saliva for the presence of drugs and opiates and comparing it to the cut-off (the quantitative threshold that’s set for the test). This type of testing is more expensive than urinalysis and blood testing. Users will test positive from a saliva test for up to 72 hours after they have consumed cannabis.

Hair Test

This type of test gives the biggest window for the detection of drugs and opiates. With the hair follicle test, laboratories test for the presence of THC in the hair follicles for up to three months. As a result, this is the most expensive form of drug testing.

Factors That Influence Drug Testing Results

Whether you have a negative or a positive result on your drug screen will depend on a few factors including:

  • The frequency of use;
  • The amount of cannabis consumed;
  • The level of tolerance in users;
  • The hydration levels of users;
  • The physical activity, metabolic rate, and BMI (body mass index) of users;
  • Other medical conditions that the users might have.

Home Drug Tests and Why Do People Take Them?

The home panel drug tests are commercially available kits that test for the presence of drug metabolites in the body. These types of tests can be bought at a lot of drugstores and people often use them as a preventive measure before taking a drug test at work, or parents use them to test their kids for drug use. 

You can find at home THC test kits for testing saliva, urine, and hair, with urine tests being the most commonly used ones. The testing kits include a collection cup, the test (a test strip, card, or cassette), and instructions for use. If the test needs further testing in a lab, some tests also contain shipping containers. In case you get a positive result, you can send your test to the lab for further analysis. Beware that tests can sometimes show false negative or false positive results. Some users report a false positive on their test as a result of using CBD oil as well as other medication. 

To get the most accurate results, users should:

  • Check the expiration date of the home test;
  • Check the window of detection for THC; 
  • Check whether the test was performed correctly;
  • Check if the person tested takes other prescription medications that might mess with the result of the test.  

Are At-Home Drug Tests Accurate?

At-home drug tests can be sensitive to the presence of drugs, and if your home test shows a positive result, that’s a good indication that your lab test would be positive too. Generally, home tests are 99% accurate if you do them according to the instructions listed on the test kit.

Although at-home test results can sometimes show a false positive or negative depending on the amount of time that has passed after consuming drugs or opiates, as well as other medications that users are taking and other relevant factors.

Home drug tests are a great way for you to see if you might test positive at your next mandatory drug screening at work, in order to know whether you have enough time for your body to detox.

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.