A toxicology test checks blood or urine for the presence of drugs. In rare cases, stomach contents, sweat, or saliva 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 sample instead of blood, because urine tests are usually easier to do than blood tests and many drugs show up in the urine. Also, traces of a drug may remain in urine for longer than in blood.

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 athletes for the use of drugs that enhance their athletic ability. This is usually done on a urine 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 medications (prescription and nonprescription), herbal supplements, vitamins, and other substances you are taking or have taken in the past 4 days.

You will need to sign a consent form that says you understand the risks of the toxicology testing and agree to have it done. Talk to your doctor about any concerns you have regarding 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?).

How It Is Done

Blood test

The health professional taking a sample of your blood will:

• Wrap an elastic band around your upper arm to stop the flow of blood. This makes the veins below the band larger so it is easier to put a needle into the vein.
• Clean the needle site with alcohol.
• Put the needle into the vein. More than one needle stick may be needed.
• Attach a tube to the needle to fill it with blood.
• Remove the band from your arm when enough blood is collected.
• Put a gauze pad or cotton ball over the needle site as the needle is removed.
• Put pressure on the site and then put on a bandage.

Clean-catch midstream urine collection