Toxicology Tests

Toxicology Tests

Test Overview

A toxicology test ("tox screen") checks for drugs or other chemicals in your blood, urine, or saliva. Drugs can be swallowed, inhaled, injected, or absorbed through the skin or a mucous membrane. In rare cases, a tox screen may check your stomach contents or sweat.

A tox screen may check for one certain drug or for up to 30 different drugs at once. These may include prescription medicines, nonprescription medicines (such as aspirin), vitamins, supplements, alcohol, and illegal drugs, such as cocaine and heroin.

Testing is often done on urine or saliva instead of blood. Many drugs will show up in a urine or saliva sample. And urine and saliva tests are usually easier to do than blood tests.

Why It Is Done

This test may be done to:

  • Find out if a drug overdose may be causing life-threatening symptoms, unconsciousness, or strange behavior. This test will be done right away in this situation. A toxicology test can also be done up to 3-4 days after a possible overdose.
  • Check for drug use in the workplace. Testing is common for people who work in public safety, such as bus drivers or child care workers. Some jobs require a toxicology screen as part of the hiring process.
  • Check for drug use in students involved in extracurricular activities, such as sports and cheerleading.
  • Look for the use of drugs that enhance athletic ability.
  • Check for the presence of a date rape drug.

How To Prepare

Many medicines can change the results of this test. So give your doctor a list of all the medicines you have taken in the past 4 days. Be sure to include any prescription and over-the-counter medicines, vitamins, and natural health products.

How It Is Done

Blood test

A health professional uses a needle to take a blood sample, usually from the arm.

Clean-catch midstream urine collection

Collecting the urine this way keeps the sample from being contaminated.

  • Wash your hands to make sure they are clean before you collect the urine.
  • If the collection cup has a lid, remove it carefully. Set it down with the inner surface up. Do not touch the inside of the cup with your fingers.
  • Clean the area around your genitals.
    • For men: Pull back the foreskin, if you have one. Clean the head of the penis thoroughly with medicated towelettes or swabs.
    • For women: Spread open the folds of skin around the vagina with one hand. Then use your other hand to clean the area around the vagina and urethra thoroughly with medicated towelettes or swabs. Wipe the area from front to back to avoid spreading bacteria from the anus to the urethra.
  • Start urinating into the toilet or urinal. Women should keep holding apart the folds of skin around the vagina while they urinate.
  • After the urine has flowed for several seconds, place the collection cup into the stream. Collect about 3 fl oz (90 mL) of this "midstream" urine without stopping the flow.
  • Do not touch the rim of the cup to your genital area. And don't get toilet paper, pubic hair, stool (feces), menstrual blood, or other foreign matter in the urine sample.
  • Finish urinating into the toilet or urinal.
  • Carefully replace the lid on the cup. Return the cup to the lab. If you are collecting the urine at home and can't get it to the lab in an hour, refrigerate it.

If you are being tested for drug use, a trained person of the same sex will watch you give the sample. This is to make sure that you are providing your own urine and that you have not added anything to the sample. The temperature of the urine may also be tested to make sure that it is fresh.

Saliva test

The person who collects the sample will either:

  • Swab the inside of your cheek, or
  • Ask you to spit into a tube.

Watch

How It Feels

Blood test

When a blood sample is taken, you may feel nothing at all from the needle. Or you might feel a quick sting or pinch.

Urine test

It is not painful to collect a urine sample. Another person may watch while you collect the sample. This may make you feel uncomfortable.

Saliva test

It is not painful to collect a saliva sample. Another person will collect the sample or watch you collect the sample.

Risks

Blood test

There is very little chance of having a problem from this test. When a blood sample is taken, a small bruise may form at the site.

Urine test

There are no known risks from having this test.

Saliva test

There are no known risks from having this test.

Results

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.

Credits

Current as of: September 23, 2020

Author: Healthwise Staff
Medical Review:
E. Gregory Thompson MD - Internal Medicine
Adam Husney MD - Family Medicine
Martin J. Gabica MD - Family Medicine
Kathleen Romito MD - Family Medicine
R. Steven Tharratt MD, MPVM, FACP, FCCP - Pulmonology, Critical Care Medicine, Medical Toxicology

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