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Test ID: UPH24 pH, 24 Hour, Urine

Reporting Name

pH, 24 HR, U

Useful For

Assessment of patients with metabolic acidosis, crystalluria, as well as monitoring the effectiveness of alkalinization or acidification of urine for certain medical conditions (eg, treatment of uric acid nephrolithiasis) using a 24-hour collection period

Clinical Information

Urine pH is a measure of the acidity/alkalinity of urine and, by itself, usually provides little useful information. Under normal conditions its value is influenced by the type of diet. Some diets (eg, diets rich in meat) have more acid content than others (eg, vegetarian diets).


Changes in urine pH may reflect systemic acid-base disorders. For example, the normal response during metabolic acidosis is a lowering of the urine pH to less than 5. If the pH is greater than 5, then a defect in urine acidification should be considered. A urine pH of greater than 8 is suggestive of infection by a urea-splitting organism such as Proteus mirabilis.


Therapeutic interventions to either alkalinize or acidify the urine are necessary for some diseases. For example, some crystals have a propensity to form in alkaline urine, while others form in relative acidic urine, and changing the pH may reduce stone formation.


Dependent on clinical condition.


A pH greater than 8 suggests the presence of urinary tract infection with a urea-splitting organism.

Report Available

1 to 3 days

Day(s) Performed

Monday through Sunday

Clinical Reference

1. Menezes CJ, Worcester EM, Coe FL, Asplin J, Bergsland KJ, Ko B: Mechanisms for falling urine pH with age in stone formers. Am J Physiol Renal Physiol. 2019 Jul 1;317(7):F65-F72

2. Ilyas R, Cho K, Young JG: What is the best method to evaluate urine pH? A trial of three urinary pH measurement methods in a stone clinic. J Endourol. 2015 Jan;29(1):70-74

3. Davidsohn I, Henry JB: Todd-Sanford Clinical Diagnosis by Laboratory Methods. 15th ed. Elsevier; 1974; 43-44

4. Free AH, Free HBS: Urodynamics, concepts relating to urinalysis. Ames Co; 1974:57-61

5. Kaplan LA, Pesce AJ: Clinical Chemistry: Theory, Analysis, Correlation. 3rd ed. Mosby-Year Book Inc; 1996:823

Method Name

pH Meter

Specimen Type


Necessary Information

24-Hour volume is required.

Specimen Required


Diazolidinyl Urea (Germall), 5.0 mL (T822)

Urine Tubes, 10 mL (T068)

Container/Tube: Plastic, 10-mL urine tube or a clean, plastic aliquot container

Specimen Volume: 10 mL

Collection Instructions:

1. Collect urine for 24 hours

2. Add 5 mL of diazolidinyl urea as preservative at start of collection or refrigerate specimen during and after collection.

3. Specimen pH should be between 4.5 and 8 and will stay in this range if kept refrigerated. Specimens with pH >8 indicate bacterial contamination, and testing will be cancelled. Do not attempt to adjust pH as it will adversely affect results.

Additional Information: See Urine Preservatives-Collection and Transportation for 24-Hour Urine Specimens for multiple collections.

Specimen Minimum Volume

1 mL

Specimen Stability Information

Specimen Type Temperature Time Special Container
Urine Refrigerated (preferred) 7 days
  Frozen  7 days

Reference Values


Test Classification

This test has been cleared, approved, or is exempt by the US Food and Drug Administration and is used per manufacturer's instructions. Performance characteristics were verified by Mayo Clinic in a manner consistent with CLIA requirements.

CPT Code Information


LOINC Code Information

Test ID Test Order Name Order LOINC Value
UPH24 pH, 24 HR, U 27378-9


Result ID Test Result Name Result LOINC Value
PH24 pH, 24 HR, U 27378-9
TM90 Collection Duration 13362-9
VL72 Volume 3167-4

Urine Preservative Collection Options

Note: The addition of preservative or application of temperature controls must occur at the beginning of the collection.







50% Acetic Acid


Boric Acid


Diazolidinyl Urea


6M Hydrochloric Acid


6M Nitric Acid


Sodium Carbonate






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