UPHB - Overview: pH, Body Fluid (2023)

Useful For

Suggests clinical disorders or settings where the test may be helpful

Indicating the presence of infections or fistulas

Verifying the effectiveness of treatment to reduce stomach pH

Diagnosing disease states characterized by abnormal stomach acidity

This test is not appropriate for measurement of pleural fluid pH as that measurement should be made using a blood gas analyzer locally due to sample stability and transport requirements.

Method Name

A short description of the method used to perform the test

pH Meter

NY State Available

Indicates the status of NY State approval and if the test is orderable for NY State clients.


Reporting Name

Lists a shorter or abbreviated version of the Published Name for a test

pH, BF


Lists additional common names for a test, as an aid in searching

Body Fluid pH

Specimen Type

Describes the specimen type validated for testing

Body Fluid

Necessary Information

1. Date and time of collection.

2. Specimen source

-Preferred: Identify source name from the following list with location (if appropriate):

-Peritoneal fluid (peritoneal, abdominal, ascites, paracentesis)

-Drain fluid (drainage, JP drain)

-Synovial fluid

-Write in source name with source location (if appropriate)

-Unacceptable: Spinal fluid (CSF), chest (thoracic) fluid, thoracentesis, pleural fluid, and urine


Question ID Description Answers
SRC18 Source Abdominal
Pancreatic Cyst Fluid

Specimen Required

Defines the optimal specimen required to perform the test and the preferred volume to complete testing

Supplies: Metal Free Specimen Vial (T173)

Container/Tube: Metal-free container

Specimen Volume: 5 mL

Specimen Minimum Volume

Defines the amount of sample necessary to provide a clinically relevant result as determined by the testing laboratory. The minimum volume is sufficient for one attempt at testing.

1 mL

Reject Due To

Identifies specimen types and conditions that may cause the specimen to be rejected

Spinal, chest (thoracic) fluid, thoracentesis, or pleural fluid

Specimen Stability Information

Provides a description of the temperatures required to transport a specimen to the performing laboratory, alternate acceptable temperatures are also included

Specimen Type Temperature Time Special Container
Body Fluid Refrigerated (preferred) 7 days
Frozen 7 days
Ambient 24 hours

Useful For

Suggests clinical disorders or settings where the test may be helpful

Indicating the presence of infections or fistulas

Verifying the effectiveness of treatment to reduce stomach pH

Diagnosing disease states characterized by abnormal stomach acidity

This test is not appropriate for measurement of pleural fluid pH as that measurement should be made using a blood gas analyzer locally due to sample stability and transport requirements.

Clinical Information

Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test

The pH value is a measure of hydrogen ion concentration. Increased metabolic activity and production of acidic byproducts (eg, lactic acid) due to infection is known to decrease pH. A variety of disease processes can alter pH values; therefore, low pH has reduced specificity. Gastric content typically has a low pH, and measurement of pH has been used to help identify gastric fluid. Determining the pH value of a body fluid may help characterize the nature of the fluid.

Reference Values

Describes reference intervals and additional information for interpretation of test results. May include intervals based on age and sex when appropriate. Intervals are Mayo-derived, unless otherwise designated. If an interpretive report is provided, the reference value field will state this.

An interpretive report will be provided.


Provides information to assist in interpretation of the test results

Normal gastric fluid has a pH below 3.0; any higher pH is abnormal.

Low peritoneal fluid pH (<7.35) may be observed in spontaneous bacterial peritonitis.(1)


Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances

Specimens should be collected, maintained anaerobically, and tested as soon after collection as possible as exposure to air and time causes pH to increase as carbon dioxide is lost from the sample.

Clinical Reference

Recommendations for in-depth reading of a clinical nature

1. Wong CL, Holroyd-Leduc J, Thorpe KE, Straus SE: Does this patient have bacterial peritonitis or portal hypertension? How do I perform a paracentesis and analyze the results? JAMA 2008;299(10):1166-1178

2. 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;317:F65-F72

3. 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. 2015:29:70-74

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

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

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

Method Description

Describes how the test is performed and provides a method-specific reference

The pH meter is composed of a glass electrode, calomel electrode and voltmeter. The glass electrode has a fixed acid concentration, yielding a corresponding voltage. The calomel electrode is the reference electrode. Its voltage is independent of the H+ ion concentration. The two electrodes constitute a galvanic cell whose electromotive force is measured by the voltmeter. The meter is calibrated to read in pH units, reflecting the H+ ion concentration. The meter is used to determine pH in 0 to 14 range.(Instruction manual: Fisher Scientific accumet Basic (AB) Benchtop Meters. Fisher Scientific; 07/2018)

PDF Report

Indicates whether the report includes an additional document with charts, images or other enriched information


Day(s) Performed

Outlines the days the test is performed. This field reflects the day that the sample must be in the testing laboratory to begin the testing process and includes any specimen preparation and processing time before the test is performed. Some tests are listed as continuously performed, which means that assays are performed multiple times during the day.

Monday through Sunday

Report Available

The interval of time (receipt of sample at Mayo Clinic Laboratories to results available) taking into account standard setup days and weekends. The first day is the time that it typically takes for a result to be available. The last day is the time it might take, accounting for any necessary repeated testing.

Same day/1 day

Specimen Retention Time

Outlines the length of time after testing that a specimen is kept in the laboratory before it is discarded

7 days

Performing Laboratory Location

Indicates the location of the laboratory that performs the test



Several factors determine the fee charged to perform a test. Contact your U.S. or International Regional Manager for information about establishing a fee schedule or to learn more about resources to optimize test selection.

  • Authorized users can sign in to Test Prices for detailed fee information.
  • Clients without access to Test Prices can contact Customer Service 24 hours a day, seven days a week.
  • Prospective clients should contact their account representative. For assistance, contact Customer Service.

Test Classification

Provides information regarding the medical device classification for laboratory test kits and reagents. Tests may be classified as cleared or approved by the US Food and Drug Administration (FDA) and used per manufacturer instructions, or as products that do not undergo full FDA review and approval, and are then labeled as an Analyte Specific Reagent (ASR) product.

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

Provides guidance in determining the appropriate Current Procedural Terminology (CPT) code(s) information for each test or profile. The listed CPT codes reflect Mayo Clinic Laboratories interpretation of CPT coding requirements. It is the responsibility of each laboratory to determine correct CPT codes to use for billing.

CPT codes are provided by the performing laboratory.


LOINC® Information

Provides guidance in determining the Logical Observation Identifiers Names and Codes (LOINC) values for the order and results codes of this test. LOINC values are provided by the performing laboratory.

Test Id Test Order Name Order LOINC Value
UPHB pH, BF 2748-2
Result Id Test Result Name Result LOINC Value

Applies only to results expressed in units of measure originally reported by the performing laboratory. These values do not apply to results that are converted to other units of measure.

U_PHB pH, BF 2748-2
SRC18 Source 14725-6
CMT36 Comment 48767-8
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