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Urine Culture

How It Feels

Collecting a urine sample does not cause pain.

Risks

There is no chance for problems while collecting a urine sample.

Results

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.

Urine culture
Normal:

No bacteria or other organisms (such as fungi) grow in the culture. The culture result is negative.

Abnormal:

Organisms (usually bacteria) grow in the culture. The culture result is positive.

A 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 antibiotics.

If test results are positive, sensitivity testing may be done to help make decisions about treatment.

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 them.
  • 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 Urine Test.
  • A urine culture may be repeated after the UTI has been treated to make sure the infection is cured.
  • A 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.
  • People 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 tap).
  • To diagnose tuberculosis that has spread to the urinary tract, a special test will be done using all of the first morning urine on three separate days.
  • 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 the culture.

WebMD Medical Reference from Healthwise

Last Updated: May 21, 2012
This information is not intended to replace the advice of a doctor. Healthwise disclaims any liability for the decisions you make based on this information.

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