Your health care provider may advise you to stop taking certain drugs that can affect the results of the test. Eat a normal, balanced diet for several days before the test.

Submit a urine sample to the laboratory. If the specimen is contaminated by vaginal discharge or bleeding, then collect a clean-catch sample. If the collection is being taken from an infant, a couple of extra collection bags may be necessary.

pH is a measure of how acidic or alkaline a fluid is, like blood or urine. The pH in blood is maintained within the narrow range of 7.35 to 7.45. Your body maintains this narrow range by using buffers -- chemicals that can switch back and forth between 2 forms, a weak acid or weak base. The buffers are only temporary "stop gaps" to avoid dramatic changes in blood pH.

Long-term correction of blood pH requires the kidneys to excrete the acid or base in urine. For example, when your blood pH is low (acidic), your kidneys react by excreting more acid in the urine. The urine pH becomes more acidic until the blood pH returns to normal.

In some cases, checking your urine pH is helpful for identifying body acid-base imbalances. In other cases, a blood pH test is needed.

Your provider may want to modify your urine pH to help prevent kidney stones. Acidic urine is associated with xanthine, cystine, uric acid, and calcium oxalate stones. Alkaline urine is associated with calcium carbonate, calcium phosphate, and magnesium phosphate stones.

Some medications are more effective in acidic or alkaline environments. For example, streptomycin, neomycin, and kanamycin are more effective in treating urinary tract infections when the urine is alkaline.

The normal values range from 4.6 to 8.0.

A high urine pH (alkaline urine) may indicate:

• Gastric suction
• Renal failure
• Renal tubular acidosis
• Urinary tract infection
• Vomiting

• Chronic obstructive pulmonary disease (e.g., emphysema)
• Diabetic ketoacidosis
• Diarrhea
• Starvation

• Alkalosis
• Interstitial nephritis
• Renal tubular acidosis - distal
• Sepsis

• A diet high in citrus fruits, vegetables, or dairy products can increase your urine pH. Some drugs also can increase urine pH, including acetazolamide, potassium citrate, and sodium bicarbonate.
• A diet high in meat products or cranberries can decrease your urine pH. Drugs that can decrease urine pH include ammonium chloride, chlorothiazide diuretics, and methenamine mandelate.
• Urine pH can be affected by various factors after collection. For example, leaving the urine standing in an uncovered container. Also, bacteria usually increase the pH as they break down urea to ammonia.