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
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
Find out if a drug overdose may be causing life-threatening
symptoms, unconsciousness, or strange behavior. It is
usually done within 4 days after a drug may have been taken.
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 tox screen as part of the hiring process.
Check for drug use in students involved in extracurricular activities, such as sports and cheerleading.
for the use of drugs that enhance athletic ability.
Check for the presence of a date
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.
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
medical test information form(What is a PDF document?).
How It Is Done
The health professional taking a sample
of your blood will:
Wrap an elastic band around your upper arm to
stop the flow of blood. This makes the veins below the band larger so it is
easier to put a needle into the vein.
Clean the needle site with
Put the needle into the vein. More than one needle stick
may be needed.
Attach a tube to the needle to fill it with
Remove the band from your arm when enough blood is
Put a gauze pad or cotton ball over the needle site as
the needle is removed.
Put pressure on the site and then put on a
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
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
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 abuse, 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:
Swab the inside of your cheek, or
Ask you to spit into a tube.
How It Feels
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.
You may get a small bruise at the site. You
can lower the chance of bruising by keeping pressure on the site for several
In rare cases, the vein may become swollen after the
blood sample is taken. This problem is called phlebitis. You can treat this by using a warm compress several times a day.
Bleeding can be a problem for people who have bleeding disorders or take blood-thinning medicines such as aspirin or warfarin (Coumadin). If you have bleeding or clotting problems, or if you take blood-thinning medicine, tell your doctor before your blood sample is taken.
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)
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 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
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
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.
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.
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
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.
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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
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
How this information was developed to help you make better health decisions.