A urine culture is a test to find and
identify germs (usually bacteria) that may be causing a
urinary tract infection (UTI). Urine in the bladder
normally is sterile—it does not contain any bacteria or other organisms (such
fungi). But bacteria can enter the
urethra and cause an infection.
sample is kept under conditions that allow bacteria and other organisms to
grow. If few or no organisms grow, the test is negative. If organisms
grow in numbers large enough to indicate an infection, the culture is
positive. The type of organisms causing the infection are
identified with a microscope or by chemical tests.
infections are more common in women and girls than in men. This may be partly
because the female urethra is shorter and closer to the
anus, which allows bacteria from the intestines to
come into contact more easily with the urethra. Men also have an antibacterial substance in their
prostate gland that reduces their risk.
If the urine culture is positive, other tests may be done to help choose
which antibiotic will do the best job treating the infection. This is called
Why It Is Done
A urine culture may be done to:
Find the cause of a urinary tract infection
Make decisions about the best treatment for a UTI. This is
called sensitivity testing.
Find out whether treatment for a UTI
How To Prepare
You do not need to do anything before
you have this test. If you are taking or have recently taken
antibiotics, tell your doctor.
need to collect a urine sample. Avoid urinating just before having this
Talk to your doctor about any concerns you have regarding
the need for the test, its risks, how it will be done, or what the results will
mean. To help you understand the importance of this test, fill out the
medical test information form(What is a PDF document?).
How It Is Done
You will be asked to collect a
clean-catch midstream urine sample for testing. The first urine of the day is
preferred because bacterial levels will be higher.
Clean-catch midstream urine collection
helps protect the urine sample from germs that are normally found on the penis
Wash your hands before collecting the
If the collection container has a lid, remove it carefully
and set it down with the inner surface up.
Clean the area around
your penis or vagina.
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
vagina and urethra thoroughly with medicated towelettes or swabs. She should
wipe the area from front to back to avoid spreading bacteria to the vagina that
is normally found around the anus.
Begin urinating into the toilet or urinal. A
woman should continue holding apart the folds of skin around the vagina while
she is urinating.
After the urine has flowed for several seconds,
place the collection container in the stream and collect about
60 mL (2 fl oz) of this
"midstream" urine without stopping the flow.
Do not touch the rim
of the container to your genital area.
Do not get toilet paper,
hair, feces, or menstrual blood in the urine sample.
urinating into the toilet or urinal.
Carefully replace the lid on
the container. Wash your hands. Return the urine sample to the lab. If you are
collecting the urine at home and cannot get it to the lab within an hour,
refrigerate the sample. It can be refrigerated for up to 24 hours. Follow the
instructions from your lab.
How It Feels
Collecting a urine sample does not cause
There is no chance for problems while collecting
a urine sample.
A urine culture is a test to detect and
identify organisms (usually bacteria) that may be causing a
urinary tract infection (UTI). Urine culture results
are usually ready in 1 to 3 days. Some organisms take longer to grow in the
culture; for this reason, results may not be available for several days.
No bacteria or other organisms (such as
fungi) grow in the culture. The culture result is
Organisms (usually bacteria) grow in the
culture. The culture result is positive.
count of 100,000 or more bacteria per
milliliter (mL) of urine may be caused by an
infection. A count ranging from 100 to 100,000 could be either caused by
infection or by contamination of the sample (you may need a repeat urine
culture). If the count is 100 or less, infection is unlikely; however, a count
of 100 or less may also be seen if you are already taking
If test results are positive,
sensitivity testing may be done to help make decisions
What Affects the Test
Reasons you may not be able to
have the test or why the results may not be helpful include:
Taking antibiotics or just finished taking
Taking water pills (diuretics) or
drinking a large amount of liquid. This may dilute your urine and reduce the
number of bacteria in the sample.
Taking a lot of vitamin C.
What To Think About
A urine culture done in the early stage of a
urinary tract infection (UTI) may be less accurate than one that is done after
the infection becomes established.
A urine culture may be done when
an abnormal result from a
urinalysis (such as an increased number of white blood
cells) shows signs of an infection. To learn more, see the topic
A urine culture may be repeated after
the UTI has been treated to make sure the infection is cured.
health professional may collect a urine sample by placing a
urinary catheter into the bladder. This method is
sometimes used to collect urine from a person in the hospital who is very ill
or unable to provide a clean-catch sample. Using a catheter to collect a urine
sample reduces the chance of getting bacteria from the skin or genital area in
the urine sample, but catheter use sometimes causes a UTI.
who have a urinary catheter in place for a long time are at high risk for
developing a UTI.
Collecting a urine sample from a small child or
baby may be done by using a special plastic bag with tape around its opening (a
U bag). The bag is attached around the child's genitals until he or she
urinates (usually within an hour). Then the bag is carefully removed. To
collect a urine sample from a very sick baby, a doctor may insert a needle
through the baby's abdomen directly into the bladder (suprapubic
tuberculosis that has spread to the urinary tract, a
special test will be done using all of the first morning urine on three
Sensitivity testing helps your doctor
choose the best medicine to treat specific types of bacteria or fungus that may
be causing a UTI.
Some types of bacteria or fungi may take several weeks to grow in
Other Works Consulted
Chernecky CC, Berger BJ (2008). Laboratory Tests and Diagnostic Procedures, 5th ed. St. Louis:
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.
E. Gregory Thompson, MD - Internal Medicine
W. David Colby IV, MSc, MD, FRCPC - Infectious Disease
How this information was developed to help you make better health decisions.