Normal fresh urine pH is between 4.5-7.9, and urine left too long is alkaline. Urine pH is one of the elements of routine urine examination, reflecting the kidney’s ability to regulate the acid-base balance of body fluids. The body can excrete a large amount of acidic and alkaline substances through urine to maintain acid-base balance. The kidneys need to excrete about 50-100mmol of fixed acid produced by food decomposition every day, so a high protein diet can produce acidic urine, and the urine is alkaline when eating vegetables containing less fixed acid. Common diseases with lower urine pH include respiratory or metabolic acidosis, diabetic ketoacidosis, gout, fever, nephritis, diarrhea, etc. Common diseases with elevated urine pH include respiratory or metabolic alkalosis, renal tubular acidosis, prolonged vomiting, loss of gastric juice, pyelonephritis, etc.”