The pH of a specimen provides an indication of the total hydrogen ions (acidic substances) the specimen contains. The metabolism (digestion) of animal proteins tends to produce acidic compounds that are mostly neutralized by basic compounds such as bicarbonates. This mechanism keeps the blood pH close to a very slightly alkaline level of 7.4. To achieve this, excess hydrogen ions in the blood must be excreted in the urine, whose pH is normally more acidic (pH 5 or pH 6).
Abnormal pH values indicate a possible disturbance in the blood’s acid-base equilibrium, as can be seen, for example, in acidosis from poorly controlled diabetes, in prolonged fasting, or following the absorption of certain medications or toxins. Bacterial infections of the urinary tract or prolonged urine specimen retention can also produce urine with an alkaline pH (pH > 7).