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Home > Fitness & Health > Health Library > Toxicology Tests
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.
This test may be done to:
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.
You will be asked to sign a consent form that says you understand the risks of the test and agree to have it done. If you are a student, your parents may also need to sign a consent form before you can be tested.
Talk to your doctor if you have any concerns about 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? ).
The health professional taking a sample of your blood will:
Collecting the urine this way keeps the sample from being contaminated.
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.
The person who collects the sample will either:
The blood sample is taken from a vein in your arm. An elastic band is wrapped around your upper arm. It may feel tight. You may feel nothing at all from the needle, or you may feel a quick sting or pinch.
It is not painful to collect a urine sample. Another person may watch while you collect the sample. This may make you feel uncomfortable.
It is not painful to collect a saliva sample. Another person will collect the sample or watch you collect the sample.
There is very little chance of a problem from having a blood sample taken from a vein.
Collecting a urine sample does not cause problems.
Collecting a saliva sample does not cause problems.
A toxicology test (tox screen) checks for drugs or other chemicals in your blood, urine, or saliva.
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.
No unexpected drugs are found in the sample.
Levels of prescription or nonprescription medicines found in the sample are within the effective (therapeutic) range.
Unexpected drugs are found in the sample.
Levels of prescription or nonprescription medicines found in the sample are:
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 levels of prescription or over-the-counter medicines may mean that you are not taking your medicine correctly.
You may not be able to have the test, or the results may not be helpful, if:
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 opioid may be identified as an opioid.
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: http://www.usantidoping.org/files/active/athletes/athlete-handbook.pdf.
World Anti-Doping Agency (210). Guidelines for Urine Sample Collection. Available online: http://www.wada-ama.org/Documents/Resources/Guidelines/WADA_Guidelines_Urine_Sample_Collection_v5.1_EN.pdf.
Current as of:
March 28, 2019
Author: Healthwise StaffMedical Review: E. Gregory Thompson MD - Internal MedicineAdam Husney MD - Family MedicineMartin J. Gabica MD - Family MedicineKathleen Romito MD - Family MedicineR. Steven Tharratt MD, MPVM, FACP, FCCP - Pulmonology, Critical Care Medicine, Medical Toxicology
Current as of:
March 28, 2019
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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