Urine Bacteria

A microscope count of how many bacteria are in your urine. A few can just be contamination, and a urine culture is the test that identifies which bacteria are present.

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What it is

Bacteria in urine are looked for when the lab examines a urine sample under a microscope. Urine normally has few or no bacteria, but a sample can pick up bacteria from the skin and genital area on the way out. Labs report the amount with words like none seen, few, moderate or many, or as a count per high-power field (HPF), which is a single view under the microscope.

Why it matters

Bacteria can be a clue to a urinary tract infection (UTI), but they don't prove one. Many samples show bacteria only because of contamination during collection, especially in women. Some people also have bacteria in their urine without any symptoms or harm, which is called asymptomatic bacteriuria. The lab and your clinician read bacteria alongside white blood cells, the nitrite and leukocyte esterase dipstick results, and your symptoms. A urine culture is the test that shows which bacteria are growing.

If it’s high

More bacteria means more were seen in the sample when it was examined. This can be linked to a urinary tract infection. It can also reflect contamination during collection, or bacteria that multiplied while the sample sat before testing. Bacteria without symptoms are common, and they are handled differently from an infection with symptoms. Your clinician will weigh the result against how you feel and your other urinalysis results.

Common causes

Contamination from the skin or vaginal area during collection, which is common in clean-catch samples from women
A sample that sat for too long, especially at room temperature, so bacteria multiplied
Asymptomatic bacteriuria, which means bacteria in the urine with no symptoms
A urinary tract infection (UTI)
A urinary catheter or an underlying problem in the urinary tract

What can help

Collect a midstream, clean-catch sample and follow the lab's cleaning and handling instructions
Get the sample to the lab promptly, or keep it refrigerated if you're told to
Tell your clinician about any symptoms, such as burning, urgency or fever, because they change how the result is read
Ask whether a urine culture would help sort out the result

What can affect your result

Collection method: a midstream clean-catch sample has less contamination than a sample taken from a catheter bag
Sex: samples from women pick up bacteria from vaginal flora more often
Time and temperature: bacteria multiply in a sample left at room temperature
Pregnancy: bacteria in the urine are looked for and managed differently during pregnancy
Reporting scale: some labs use words (none, few, moderate, many) and others use counts per high-power field, and these scales differ between labs
Contamination from skin or vaginal flora during collection is a common reason bacteria show up, and it is more frequent in clean-catch samples from women.
Bacteria keep multiplying in a sample left at room temperature, which can raise the count. One large lab accepts unpreserved urine for 2 hours at room temperature or 48 hours refrigerated.
A sample taken from a urinary catheter bag is considered contaminated and shouldn't be used.

A midstream clean-catch sample, first-morning or random. Test it within 1–2 hours of collection, or refrigerate it. It reflects the sample at the moment of collection. It can change quickly, within hours to days, as an infection starts or clears.

When to talk to a clinician

Bacteria on a urinalysis with no symptoms isn't usually urgent. Contact a clinician soon if you have burning when you urinate, a need to go often or urgently, lower belly pain or blood in your urine. Get prompt care for fever or chills, back or side pain, nausea or vomiting, or confusion along with urinary symptoms. If you're pregnant, tell your clinician about any bacteria on a urine test.

Questions you could ask

Is there anything I should do differently when I collect my next sample?
Does being pregnant, having a catheter or having urinary problems change how you read bacteria in my urine?
Could this result be from contamination, and should the sample be repeated?
Would a urine culture help sort this out?
Do my symptoms and my white blood cell and nitrite results change how you read this?

Questions people ask

Does 'bacteria' on my urinalysis mean I have a UTI?

Not necessarily. Bacteria can come from contamination during collection, and some people have bacteria in their urine without symptoms. Clinicians look at your symptoms, white blood cells and the nitrite and leukocyte esterase dipstick results, and a urine culture can confirm what's growing.

Why does my report show bacteria when I feel fine?

Contamination is a common reason, especially with clean-catch samples from women. Some healthy people also carry bacteria in their urine without symptoms, called asymptomatic bacteriuria. Guidelines treat this differently from a UTI with symptoms, and pregnancy is a special case, so mention it to your clinician if it applies.

What is the difference between a urinalysis and a urine culture?

A urinalysis uses a dipstick and a microscope to take a quick look at the sample. A culture grows any bacteria in the lab so they can be identified and counted, which takes longer. The culture is the test that confirms which bacteria are present.

How can I lower the chance of a contaminated sample?

Wash your hands and follow the cleaning steps in your collection kit. Let a little urine go into the toilet first, then collect the middle of the stream in the container. This is called a midstream clean-catch. Your lab's instructions come first, and the sample should reach the lab quickly or be refrigerated as directed.

Are the nitrite and leukocyte esterase results more helpful than the bacteria count?

They answer different questions. Nitrite reacts to certain kinds of bacteria, and leukocyte esterase reacts to white blood cells. Clinicians usually read all of these together with your symptoms, because no single result settles it.

Show the science and sources

For clinicians and researchers

Bacteria are counted in the urine sediment on microscopy, usually per high-power field (HPF), or by automated sediment analyzers, and are reported semi-quantitatively (none, rare, few, moderate, many) or as a count. AFP (2005) notes that in clean-catch specimens from women, which are often contaminated by vaginal flora, about five bacteria per HPF corresponds to roughly 100,000 CFU/mL, and that any bacteria in a properly collected male specimen suggests infection and warrants culture. Its summary of studies of culture-confirmed UTI gives microscopic bacteria (any amount) a sensitivity of 46–58% and a specificity of 89–94%, compared with leukocyte esterase (sensitivity 72–97%) and nitrite (sensitivity 19–48%, specificity 92–100%). AFP also advises that Gram stain is not indicated in routine outpatient practice. Bacterial overgrowth in a standing specimen can cause false-positive dipstick blood results and shift the pH (StatPearls). The IDSA guideline on asymptomatic bacteriuria (2019 update) covers when bacteriuria without symptoms is and isn't treated, and pregnancy and certain urologic procedures are handled differently from other situations. The urine culture remains the reference test for identifying and counting organisms.

LOINC 5769-5 (primary), 25145-4, 33218-9. Specimen: urine.

Sources

Urinalysis, StatPearls Publishing (NCBI Bookshelf) (2023)
Urinalysis: A Comprehensive Review, American Family Physician (2005)
Clinical Practice Guideline for the Management of Asymptomatic Bacteriuria: 2019 Update by the Infectious Diseases Society of America, Clinical Infectious Diseases (2019)
Urinalysis, Complete With Microscopic Examination (test 003772), Labcorp

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