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Toxicology Tests

A toxicology test checks blood, urine, or saliva for the presence of drugs or chemicals. In rare cases, stomach contents or sweat may also be checked.

Drugs can be accidentally or deliberately swallowed, inhaled, injected, or absorbed through a skin surface or mucous membrane. These include prescription medicines, nonprescription medicine (such as aspirin or acetaminophen), vitamins, nutritional supplements, alcohol, and illegal drugs, such as cocaine and heroin.

A toxicology test may check for one specific drug or for up to 30 different drugs at once. Testing is often done on a urine or saliva sample instead of blood, because urine and saliva tests are usually easier to do than blood tests and many drugs show up in either urine or saliva. Traces of a drug may remain in urine longer than in blood. Urine tests often can detect drug use within the last 5 days. Saliva testing can detect drugs used within the past day.

Why It Is Done

A toxicology test ("tox screen") can be done to:

  • Help find the cause of life-threatening symptoms, unconsciousness, or bizarre behavior in an emergency situation. It is usually done within 96 hours (4 days) after a drug may have been taken. The toxicology test is used to find out if symptoms may be caused by a drug overdose. Both a urine sample and a blood sample may be tested.
  • Test for drug use in the workplace, especially for people who are involved with public safety, such as bus drivers or child care workers. A toxicology test may also be a normal part of the application procedure for some jobs. This may be done on either a blood or urine sample.
  • Test for drug use among middle school and high school students involved in competitive extracurricular activities. Such activities include athletics, cheerleading, choir, band, and foreign language clubs.
  • Test athletes for the use of drugs that enhance their athletic ability. This is usually done on a urine or saliva sample.
  • Evaluate the possible use of date rape drugs. This is usually done on a urine sample.

How To Prepare

Many medicines may change the results of this test. Be sure to tell your doctor about all the nonprescription and prescription medicines you take. Make a list of any medicines (prescription and nonprescription), herbal supplements, vitamins, and other substances you are taking or have taken in the past 4 days.

You will be asked to sign a consent form that says you understand the risks of the test and agree to have it done. If you are a student involved in competitive extracurricular activities, your parents may also need to sign a consent form before you can be tested.

Talk to your doctor about any concerns you have about the need for the test, its risks, how it will be done, or what the results may mean. To help you understand the importance of this test, fill out the medical test information form(What is a PDF document?).

WebMD Medical Reference from Healthwise

Last Updated: November 07, 2011
This information is not intended to replace the advice of a doctor. Healthwise disclaims any liability for the decisions you make based on this information.

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