Test Directory

Clear All
Test Code
OSMOF
Test Name
Osmolality, Fecal
CPT Codes
84999
Expected Turnaround Time
2 - 4 days
Clinical Utility

Distinction of osmotic from nonosmotic secretory diarrhea. A large deficit (>50 mOsm/kg) in the calculated osmolality (twice the sum of the stool sodium and stool potassium) from the measured stool osmolality indicates osmotic diarrhea.
Specimen and Container Info

Specimen Type: Liquid Stool

Collection Container: Sterile Container

Desired Specimen Volume: 15 mL
Collection Instructions
  1. Collect liquid stool in a sterile container.
  2. Stool sample must be collected without addition of water.
Processing and Submission Instructions
  1. Transfer 15 mL of liquid stool in the original collection container.
Transport Instructions

Transport to the laboratory frozen. 
Stability Requirements

Frozen

14 days
Causes for Rejection
  • Stool not liquid
  • Stool contaminated with urine
  • Paint can submitted
  • Non-frozen stool
Methodology
Freezing-Point Depression
Reference Intervals

See patient report.
Alternate Names
  • Fecal Osmolality
Reference Lab
Labcorp Of America Holdings
Testing Schedule
Routine, Monday - Saturday
The American Medical Association (AMA) Current Procedural Terminology (CPT) codes published by HNL Lab Medicine are guidelines and are intended for informational purposes only. CPT coding is the exclusive responsibility of the billing entity. View the Terms.
© 2026 HNL Lab Medicine. All rights reserved.