Because urine contains certain acidic groups or basic groups, urine can show acidic expression or basic expression. The pH of urine is affected by drugs, food and disease. For example, when a specimen of urine is retained, if the urine specimen is left for too long, bacteria can break down the urea in the urine, thus turning the acidic urine into alkaline urine. Therefore, for the determination of urine pH, fresh urine must be applied for testing to avoid the negative effects of specimen placement. Diet can affect urine pH, for example, urine from meat eaters is generally acidic, while urine from vegetarians is generally alkaline. A urine pH of 7.0 is within the normal range, as the normal value of urine fluctuates around 6.5 and can fluctuate between 4.5 and 8.0. Some diseases can cause the pH of urine to change, for example, when acidic urine occurs, it is often seen in acidosis, hyperthermia, diabetes and the application of drugs such as ammonium chloride and vitamin C. Acidic urine can occur in low potassium and low chloride alkalosis. Alkaline urine is often seen in infections of the urinary tract, and alkaline urine can also occur in renal tubular acidosis. Urine pH testing allows adjustment of urine pH to treat related diseases, for example, in stone treatment by alkalinizing urine or acidifying urine depending on the composition of the stone.