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    Toxicology Tests

    What To Think About

    • In general, urine tests are better than blood tests at finding drugs. 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 tests can detect drugs just as well as urine and blood tests do, and they are less invasive than blood tests. (This means they don't require a needle stick.) A saliva test can detect drugs used within the past day.
    • Tox screen results are not always accurate. Sometimes a test may not find drugs that have been taken (false-negative result). Or a test may find drugs when they have not been taken (false-positive result).
    • Trying to change test results by drinking large amounts of water or taking other substances can be dangerous. And it usually doesn't change the results.
    • A test result that shows drug use or abuse can have serious outcomes, such as arrest or job loss. But the test result may not be accurate. So a positive result should always be confirmed by at least two different test methods.
    • A standard tox screen can't detect inhalant abuse, when someone sniffs common household products to "get high." Such products include glues, nail polish remover, lighter fluid, spray paints, and cleaning fluids.
    • A breath test may be used to estimate blood alcohol level. To learn more, see the topic Self-Test for Breath Alcohol.

    Other Works Consulted

    • Chernecky CC, Berger BJ (2013). Laboratory Tests and Diagnostic Procedures, 6th ed. St. Louis: Saunders.

    • Fischbach FT, Dunning MB III, eds. (2009). Manual of Laboratory and Diagnostic Tests, 8th ed. Philadelphia: Lippincott Williams and Wilkins.

    • Pagana KD, Pagana TJ (2010). Mosby’s Manual of Diagnostic and Laboratory Tests, 4th ed. St. Louis: Mosby Elsevier.

    • U.S. Anti-Doping Agency (2011). Athlete Handbook. Available online:

    • World Anti-Doping Agency (210). Guidelines for Urine Sample Collection. Available online:

    ByHealthwise Staff
    Primary Medical ReviewerE. Gregory Thompson, MD - Internal Medicine
    Specialist Medical ReviewerR. Steven Tharratt, MD, MPVM, FACP, FCCP - Pulmonology, Critical Care Medicine, Medical Toxicology

    Current as ofSeptember 9, 2014

    1 | 2 | 3 | 4 | 5

    WebMD Medical Reference from Healthwise

    Last Updated: September 09, 2014
    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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