Urinalysis test strips work by changing colors in various sections, depending on the substance with which they interact, reports PubMed Health. The strips are dipped into an individual's urine sample, and the resulting colors in the sections of the strip are compared against a color table.
The color table, which comes with the test package, allows a diagnostician to see if levels of important substances in the body are normal or not in the urine, according to PubMed Health. Urine strips can test for substances not usually found in the urine or only found in it at lower levels, and which may indicate an underlying condition. For example, urine strips measure the urine sample's pH level, or the level of acidity. The normal pH value for urine is between 5 and 7. Below-normal pH levels puts the patient at risk for developing urinary stones, and above-normal levels could be a sign of a urinary tract infection.
The presence of other substances tested by urine strips include protein, white blood cells and ketones, says PubMed Health. High levels of protein in the urine are indicative of kidney inflammation. White blood cells in the urine are a sign of a bacterial infection, and ketones or sugars are a sign of elevated blood sugar.