A toxicology test checks blood, urine, or saliva for
the presence of drugs or chemicals. In rare cases, stomach contents or sweat may
also be checked.
Drugs can be accidentally or deliberately
swallowed, inhaled, injected, or absorbed through a skin surface or
mucous membrane. These include prescription medicines,
nonprescription medicine (such as aspirin or acetaminophen), vitamins,
nutritional supplements, alcohol, and illegal drugs, such as cocaine and
A toxicology test may check for one specific drug or for
up to 30 different drugs at once. Testing is often done on a urine or saliva sample
instead of blood, because urine and saliva tests are usually easier to do than blood tests
and many drugs show up in either urine or saliva. 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 testing can detect drugs used within the past day.
Why It Is Done
A toxicology test ("tox screen") can be
Help find the cause of life-threatening
symptoms, unconsciousness, or bizarre behavior in an emergency situation. It is
usually done within 96 hours (4 days) after a drug may have been taken. The
toxicology test is used to find out if symptoms may be caused by a drug
overdose. Both a urine sample and a blood sample may be
Test for drug use in the workplace, especially for people
who are involved with public safety, such as bus drivers or child care workers.
A toxicology test may also be a normal part of the application procedure for
some jobs. This may be done on either a blood or urine sample.
Test for drug use among middle school and high school students involved in competitive extracurricular activities. Such activities include athletics, cheerleading, choir, band, and foreign language clubs.
athletes for the use of drugs that enhance their athletic ability. This is
usually done on a urine or saliva sample.
Evaluate the possible use of date
rape drugs. This is usually done on a urine sample.
How To Prepare
Many medicines may change the results
of this test. Be sure to tell your doctor about all the nonprescription and
prescription medicines you take. Make a list of any medicines (prescription and
nonprescription), herbal supplements, vitamins, and other substances you are
taking or have taken in the past 4 days.
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 involved in competitive extracurricular activities, your parents may also need to sign a consent form before you can be tested.
Talk to your doctor about any concerns you have
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
testing for drug abuse, another person will watch you to make sure that the
sample you are providing is your 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 a fresh sample.
This collection method prevents
contamination of the sample. Wash your hands to make sure they are clean before
collecting the urine.
If the collection container has a lid, remove
it carefully and set it down with the inner surface up. Do not touch the inside
of the container with your fingers.
Clean the area around your
A man should retract the foreskin, if
present, and clean the head of his penis thoroughly with medicated towelettes
A woman should spread open the folds of skin around her
vagina with one hand, then use her other hand to clean the area around her
urethra thoroughly with medicated towelettes or swabs.
She should wipe the area from front to back to avoid contaminating the urethra
with bacteria from the
Begin urinating into the toilet or urinal. A
woman should continue holding apart the folds of skin around the vagina while
After the urine has flowed for several seconds, place
the collection container into the stream and collect about
3 fl oz (90 mL) of this
"midstream" urine without stopping the flow.
Do not touch the rim
of the container to your genital area, and avoid getting toilet paper, pubic
hair, stool (feces), menstrual blood, or other foreign matter in the urine
Finish urinating into the toilet or
Carefully replace the lid on the container and return it to
the lab. If you are collecting the urine at home and cannot get it to the lab
within an hour, refrigerate the sample.
The person who collects a sample of your saliva will do it in one of the following ways:
Swabbing the inside of your cheek
Asking 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.
There is no pain while collecting a
urine sample. A trained person of the same sex may need to watch you during the
urine collection. This may make you feel uncomfortable.
There is no pain while collecting a saliva sample. A trained person will be present to either 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. A warm compress can be
used several times a day to treat this.
Ongoing bleeding can be a
problem for people with bleeding disorders. Aspirin, warfarin (Coumadin), and
other blood-thinning medicines can make bleeding more likely. If you have
bleeding or clotting problems, or if you take blood-thinning medicine, tell
your doctor before your blood sample is taken.
There is no chance for problems while
collecting a urine sample.
There is no chance for problems while
collecting a saliva sample.
A toxicology test examines blood, urine, or saliva for the presence of drugs. Most toxicology tests determine only the
presence of drugs (called qualitative testing) in the body and not the specific
level or quantity. Follow-up testing is often required to determine the exact
level of a certain drug in the body (called quantitative testing) and to
confirm the results of initial testing.
No unexpected drugs are found in the blood, urine, or saliva.
Levels of prescription or nonprescription medicines
found in the blood, urine, or saliva are within the effective (therapeutic)
Unexpected drugs are found in the blood, urine, or saliva.
Levels of prescription or nonprescription medicines
found in the blood, urine, or saliva are too low or too high to be effective
(therapeutic) or potentially toxic, if too high.
High levels of prescription or
nonprescription medicines may be caused by a drug overdose, either accidental
or intentional. 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 if you start taking a new medicine. A high level may mean that a person is not
taking his or her medicine correctly or that the medicine is not being properly
processed by the body.
Low levels of prescription or
nonprescription medicines may mean that a person is not taking his or her
What Affects the Test
Reasons the results may not be
Some drugs that may be mistaken for others. For
example, some cough medicines that do not contain
narcotics may be identified as a
Drinking or eating some types of food (such as a food
containing poppy seeds).
Having blood in the urine.
The amount of time between taking the drug and collecting the
Not having a large enough urine sample.
Many medicines may change the results of this test. Be sure
to tell your doctor about all the nonprescription and prescription medicines
What To Think About
In general, laboratory methods are better able
to detect drugs in urine than in blood. Compared to urine and blood tests, saliva tests can provide a less invasive and equally accurate way to detect drugs.
The reliability of toxicology tests
depends on the methods used by the laboratory. Occasionally drugs that have
been taken are not detected (called a
false-negative result) or drugs that have not been
taken are detected (called a
mean drug use or abuse should always be confirmed by at least two different
test methods because of the possibility of false results, the possible
consequences (such as arrest or loss of a job), and the legal aspects of drug
Attempts to block or interfere with test results by drinking
large amounts of water or taking other substances may be dangerous and usually
do not change the test results.
For suspected drug abuse, a trained
person may need to watch the urine, blood, or saliva collection, and every person who
handles the sample must sign a "chain of custody" document that is kept
together with the test report. This prevents the substitution or loss of the
urine, saliva, or blood sample.
Standard tests can't detect inhalant abuse. Inhalant abuse is when someone inhales or sniffs common household products to "get high." Such products include—but are not limited to—glues, nail polish remover, lighter fluid, spray paints, and cleaning fluids.
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
Primary Medical Reviewer
E. Gregory Thompson, MD - Internal Medicine
Specialist Medical Reviewer
R. Steven Tharratt, MD, MPVM, FACP, FCCP - Pulmonology, Critical Care Medicine, Medical Toxicology
How this information was developed to help you make better health decisions.