Esophageal pH Monitoring via Ambulatory Monitoring Study (24-Hour)
This test measures how often stomach acid flows backward into your esophagus over 24 hours to help diagnose conditions like acid reflux or gastroesophageal reflux disease (GERD).
["This test helps doctors understand if stomach acid is causing discomfort or damage to your esophagus."]
Key facts at a glance
- LOINC
- 98858-4
- Short code
- Esophageal pH monitoring study Doc
- Synonyms
- Esophageal pH monitoring study Doc
- Category
- chemistry
- Sample
- serum
- Container
- Red-top tube (SST)
- Units
- N/A
- Ref low
- 44
- Ref high
- 147
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 18–65 years
- CPT
- 84075
- SNOMED
- 27550007
- Specimen volume
- 5 mL
- Stability
- Room temperature: 4h, Refrigerated: 24h, Frozen: 7d
- Hemolysis max
- 500
- Lipemia max
- 1000
- Icterus max
- 500
- TAT
- 4–24 hours
- Order
- routine
What Does This Test Measure?
The test involves wearing a small, waterproof sensor attached to your chest that records the acidity (pH) of the esophagus throughout the day and night. It captures how often and how far acid moves backward into your esophagus, which can indicate abnormal reflux patterns.
Why Is This Test Needed?
Your doctor may recommend this test if you have symptoms like heartburn, chest pain, difficulty swallowing, or persistent coughing, even after trying over-the-counter medications. It helps rule out GERD or other conditions affecting the esophagus.
How Is the Test Performed?
You’ll wear a sensor for about 24 hours while going about your normal activities. The sensor is placed near your upper chest and connected to a small recorder you carry with you. You’ll need to keep a diary of your meals, medications, and symptoms to help analyze the results.
What Happens After the Test?
After removing the sensor, the recorder is sent to a lab for analysis. Your doctor will review the results to determine if your symptoms are linked to acid reflux or another condition. Follow-up may include lifestyle changes, medications, or further testing if needed.
Reference range
Adult: 44-147 U/LN/A
No special preparation required. Avoid fatty meals before the test if possible.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
Clinical Significance: This test is critical for diagnosing conditions like GERD, Barrett’s esophagus, or esophageal strictures by providing detailed, continuous data on acid exposure in the esophagus. It helps doctors tailor treatment plans, such as medication adjustments or dietary modifications, to improve symptoms and prevent complications.
Short name
24-Hour pH Monitoring
Frequently asked questions
What can I expect during the test?
How long does the test take?
Will I need to avoid certain foods or activities before the test?
Sources
- 1
- 2Lab Tests OnlineSource
- 3
Click any link to access the full source. PubMed Central (PMC) links provide free full-text access.
This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.
This content is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you have about a medical condition, and never disregard professional medical advice or delay seeking it because of something you read here.
If you think you may have a medical emergency, call your local emergency number or go to the nearest emergency department immediately.
Medically reviewed by WellAlly Editorial Team Last reviewed August 16, 2026. · Read our editorial policy