Is urine sterile?


Quick Answer

Urine is not sterile before or after it leaves the human body. Bacteria are always present in urine at very low concentrations. These bacteria are found in the bladder and help reduce the risk of bladder infections and urinary infections.

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Full Answer

Urine was believed to be sterile during the 1950s. It was at this time that epidemiologist Edward Kass developed the midstream urine test. He also set a numerical value for the number of bacteria that should be present in the urine samples. He considered anything below his threshold number of 100,000 colony-forming units of bacteria to be negative for bacteria. Therefore, he concluded that many patients tested negative for bacteria and had sterile urine.

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