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Toxicology Tests

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Most tox screens are qualitative tests. This means they only find out if drugs are present in the body, not the exact level or quantity. Follow-up quantitative testing is often done to find the level of a drug in the body and to confirm the results of the first test.

Toxicology tests
Normal:

No unexpected drugs are found in the sample.

Levels of prescription or nonprescription medicines found in the sample are within the effective (therapeutic) range.

Abnormal:

Unexpected drugs are found in the sample.

Levels of prescription or nonprescription medicines found in the sample are:

  • Below the effective (therapeutic) range, or
  • Above the therapeutic range, or
  • High enough that they may be toxic.

High values

High levels may be caused by a drug overdose, either by accident or on purpose. A drug overdose may be caused by one large dose of medicine or long-term overuse of a medicine.

Interactions between medicines also can cause problems, especially when you start to take a new medicine. A high level may mean that you are not taking your medicine correctly or that your body is not processing the medicine as it should.

Low values

Low levels of prescription or over-the-counter medicines may mean that you are not taking your medicine correctly.

What Affects the Test

You may not be able to have the test, or the results may not be helpful, if:

  • You drink or eat some types of food (such as a food that contains poppy seeds).
  • You have blood in your urine.
  • There is too much time between taking the drug and collecting the sample.
  • You don't give a large enough urine sample.

Many medicines may change the results of this test. And the test may mistake some drugs for others. For example, some cough medicines that do not contain an opiate may be identified as a narcotic.

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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