Urine Culture

Also written as: Urine C&S, Culture and sensitivity

Grows bacteria from a urine sample to confirm an infection and identify the organism.

What it measures

Whether bacteria or yeast grow from a urine sample over a day or two in the lab. When something grows, the lab identifies the organism and usually tests which antibiotics it is sensitive to.

Why a doctor orders it

Ordered to confirm a suspected urinary tract infection and identify the organism behind it. It is also used when symptoms keep returning, when a first course of treatment did not settle things, and routinely at certain points in pregnancy.

What is generally associated with a higher result

A culture is reported as growth rather than a number. Growth is broadly associated with urinary tract infection, but small or mixed growth often reflects skin bacteria that entered the sample during collection. Bacteria can also live quietly in the bladder without causing illness, which is called asymptomatic bacteriuria.

What is generally associated with a lower result

No growth is the expected result. Antibiotics taken recently can suppress growth even when bacteria are present.

Everyday things that move this number

Not every shift in a value reflects disease. These are ordinary factors known to affect this particular measurement:

How the sample was collected - clean-catch technique reduces contamination
A sample left at room temperature, which lets stray bacteria multiply
Antibiotics taken shortly before the sample
Very dilute urine from heavy fluid intake

Questions to take to your appointment

Was this a clean-catch sample, and could contamination explain the result?
Which organism grew, and was sensitivity testing done?
Does mixed growth mean the sample should be collected again?

Build a printable questionnaire with your own results →

Where to read more

MedlinePlus, from the US National Library of Medicine, publishes patient-facing pages on individual lab tests and is a reliable next stop: medlineplus.gov/lab-tests .

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