Lab Tests

Urine testing

This is the most common, cheapest and easiest way to test for drugs. Drugs circulate in the blood and are deposited in the bladder. It may take a few hours to show in the urine. This test can be done at a clinic or doctor's office.

Parents can do a home test called the Instant Home Drug Test, which uses a urine sample. This is a small tool that looks like a credit card, which is dipped into the urine sample, and the test works similarly to a home pregnancy test. You know the results after a few minutes on an easy-to-read test strip. The test is 96 percent accurate. Tests can detect marijuana, cocaine, amphetamines, heroin, benzodiazepines and methamphetamines.

Bear in mind that the drug may give a false-positive result, which means the test says the urine shows signs of drug abuse when the teen may not have used any. Certain prescription diet aids can cause a false positive.

By the same token, a test result could come up negative, meaning the child has not done any drugs, when in actuality the teen has done drugs. This is called a false negative, which can happen if the urine sample has been tainted or diluted. Also, there may not be enough of the drug in the urine to be picked up by the test. Drugs do not appear in the urine at the same rate. Cocaine may show up an hour after use while PCP may take as long as seven hours.

Some drugs such as Vicodin® (hydrocodone) may not be detected easily and may give you a false negative result. If your child's behavior makes you suspect drug abuse and the test result is negative, talk to a health care professional immediately.

Hair analysis

Hair cells may be more accurate when testing for drug use. Chemical properties of drugs are stored in hair cells for months because of how slowly hair grows. No matter how much shampooing, sun and bleach someone does, testing still shows drug use and can give a drug history of the past six months.

Blood testing

Blood testing is the most accurate type of drug testing done, but also the least common. Blood testing is expensive and intrusive, while urine testing is more convenient, less intrusive and the least costly of all testing methods.

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This article was reviewed and updated June 2007.