What is a Drug Test?
A drug test looks for signs of one or more illegal or prescription drugs in a sample of your urine (pee), blood, saliva (spit), hair, or sweat. The purpose of a drug test is to look for drug use and misuse, which includes:
- Using any illegal drugs, such as cocaine or club drugs
- Misusing prescription medicines, which means taking prescription medicines in a different way or for a different purpose than your provider prescribed. Examples of drug misuse include using a prescription pain reliever to relax or taking someone else's prescription.
A drug test can check for a single drug or for a group of drugs in your body. Drug tests commonly test for:
- Amphetamines, including methamphetamine
- Barbiturates, such as phenobarbital and secobarbital
- Benzodiazepines, such as alprazolam or clonazepam
- Marijuana (THC)
- Opioids and opiates, such as heroin, codeine, oxycodone, morphine, hydrocodone, and fentanyl
- Phencyclidine (PCP)
Most drug tests use urine samples. These tests can find signs of drugs within hours to several days or more before the test. How long a drug lasts in your body depends on:
- The type of drug
- How much you used
- How long you were using it before the test
- How your body reacts to the drug
Other names: drug screen, drug test, drugs of abuse testing, substance abuse testing, toxicology screen, tox screen, sports doping tests
What is it used for?
Drug testing is used to find out whether you have been using or misusing one or more drugs. But it can't diagnose a drug use disorder (addiction).
A drug test may be used for different purposes, including:
- Employment. Employers may screen you for drugs before hiring you. After you're hired, they may test you to check for on-the-job drug use. If you have a work accident, you may be tested to see whether drugs or alcohol were involved.
- Sports. Professional and other athletes are often tested for drugs that are used to improve performance, such as steroids that help build muscle.
- Drug treatment. Drug testing may be used to monitor treatment in programs for drug or alcohol use disorder.
- Legal evidence. Testing may be part of a criminal or motor vehicle accident investigation. Drug screening may also be ordered as part of a court case.
- Monitoring misuse of prescription drugs. If your provider prescribed a medicine that can be addictive, such as an opioid for long-term pain, your provider may order a drug test to make sure you're taking the medicine correctly.
Drug testing may be scheduled ahead of time or done randomly without notice.
Why do I need a drug test?
You may be asked to take a drug test for a job, to participate in certain organized sports, or as part of a police investigation or court case. In a hospital emergency room, a provider may order a drug test if you have signs of a possible drug overdose.
What happens during a drug test?
Drug testing may be done in a variety of locations, including labs, hospitals, drug treatment centers, and workplaces. The most commonly used drug tests require that you give a urine sample. You will be given instructions for how to collect your sample.
In certain cases, a health care professional or other person may need to be present while you provide your sample. This is to make sure the urine is yours and isn't contaminated with anything that might affect the test results.
For a blood test for drugs, a health care professional will take a blood sample from a vein in your arm, using a small needle. After the needle is inserted, a small amount of blood will be collected into a test tube or vial. You may feel a little sting when the needle goes in or out. This usually takes less than five minutes.
Will I need to do anything to prepare for the test?
Be sure to tell the testing professional if you are taking any prescription drugs, over-the-counter medicines, or supplements, because these substances may affect your test results. Also, you should avoid foods with poppy seeds, which can show up as opiates in a drug test.
Are there any risks to the test?
There are no known physical risks to having a drug test. But if drugs show up in your results, it may affect your job, your eligibility to play sports, the outcome of a legal matter, or other parts of your life.
Before you take a drug test, make sure you know:
- What you are being tested for
- Why you are being tested
- How the results will be used.
If you have questions or concerns about a drug test, talk with your provider or the person or organization that is asking for the test.
What do the results mean?
If a drug test result is negative, it means that either:
- The drugs that were tested were not found in the sample.
- A very small amount of drugs were found, but not enough to be a positive test result for drugs.
If a drug test result is positive, it means that one or more drugs were found in amounts that suggest drug use or misuse. Positive tests require follow-up testing because they may be wrong (false positives). The follow-up test is usually a test that provides more accurate results.
Learn more about laboratory tests, reference ranges, and understanding results.
Is there anything else I need to know about a drug test?
If you test positive for a legal drug prescribed by your doctor, your employer can't penalize you, unless the drug is affecting your ability to perform your job.
If you test positive for marijuana and live in a state where it is legal, employers may still be able penalize you. Many employers want to maintain a drug-free workplace. Also, marijuana is still illegal under federal law.
You can buy home tests for many illegal and prescription drugs. There are two types of tests:
- At-home tests let you do the entire test at home and get rapid results. But if the test result is positive for drugs, you'll need to have a follow-up lab test to check the accuracy of the result. Some at-home tests include a kit for collecting a sample, often urine or saliva, to send to a lab in case the home test is positive.
- A self-collection test has a kit for gathering urine, saliva, or another type of sample to send to a lab for testing. Some self-collection tests include the cost of a second lab test to check the accuracy of a first test that has positive results.
When using home tests, be careful to follow all the instructions. It's best to talk with your provider about using home drug testing so you can decide if it's right for your situation.
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- Drugs.com [Internet]. Drugs.com; c2000–2022. Drug Testing FAQs [updated 2019 Sep 5; cited 2022 Mar 22]; [about 11 screens]. Available from: https://www.drugs.com/article/drug-testing.html
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- Testing.com [Internet]. Seattle (WA): OneCare Media; c2022. Urine Drug Tests; [modified 2021 Nov 9; cited 2022 Mar 25]; [about 16 screens]. Available from: https://www.testing.com/tests/urine-drug-test/
- University of Rochester Medical Center [Internet]. Rochester (NY): University of Rochester Medical Center; c2022. Health Encyclopedia: Amphetamine Screen (Urine) [cited 2022 Mar 23]; [about 4 screens]. Available from: https://www.urmc.rochester.edu/encyclopedia/content.aspx?contenttypeid=167&contentid=amphetamine_urine_screen
- University of Rochester Medical Center [Internet]. Rochester (NY): University of Rochester Medical Center; c2022. Health Encyclopedia: Cannabinoid Screen and Confirmation (Urine) [cited 2022 Mar 23]; [about 2 screens]. Available from: https://www.urmc.rochester.edu/encyclopedia/content.aspx?contenttypeid=167&contentid=cannabinoid_screen_urine
- Workplace Fairness [Internet]. Silver Spring (MD): Workplace Fairness; c2022. Drug Testing; [cited 2022 Mar 23]; [about 5 screens]. Available from: https://www.workplacefairness.org/drug-testing-workplace
The information on this site should not be used as a substitute for professional medical care or advice. Contact a health care provider if you have questions about your health.