Why does my urine come back contaminate?

The best way to collect urine yourself for evaluation is to wipe with the cleansing wipe from the front back to remove some of the bacteria from the skin, urinate to flush what is climbed up the urethra before putting the sample in the cup to collect the midstream urine. You cannot collect from a dirty container to put in the cup because you have usually a clean or sterile cup to collect sample.

Relatively common, it has to do with the preparation prior to getting the urine sample, but it can also precede an actual infection, almost always seen in patients with urinary catheters.

It is not uncommon in women. Visit this site for instruction on collecting urine cleanly: https://medlineplus.gov/ency/article/007487.htm