Since bacteria, cells, and other particles can readily contaminate urine, it is advisable to wash the genital area with water, not soap, before providing a sample. Using "clean" midstream urine is necessary to obtain an accurate result and prevent bacterial contamination.
By stopping the flow of pee after a few seconds and collecting this middle section of the urine in a cup, you may obtain a sample of midstream urine. If there is anything more you need to be aware of for your particular test, your doctor will let you know.