Endoscopic evaluation of esophageal pH (24-hour ambulatory monitoring)
This test measures how much acid is in your stomach over a 24-hour period while you go about your normal activities. It helps diagnose conditions like acid reflux or GERD (gastroesophageal reflux disease).
["This test helps determine if stomach acid is flowing back into your esophagus too often, which can cause discomfort or damage."]
Key facts at a glance
- LOINC
- 111935-3
- Short code
- Site Esoph Endscpy
- Synonyms
- Site Esoph Endscpy
- Category
- chemistry
- Sample
- serum
- Container
- Red-top tube (SST)
- Units
- N/A
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 18–65 years
- Method
- endoscopy
- 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 placing a small, flexible tube with a pH sensor through your nose and down into your stomach. The sensor records acid levels continuously over 24 hours, capturing how often stomach acid reaches your esophagus.
Why Is This Test Important?
By tracking acid levels over time, doctors can assess whether you have chronic acid reflux or other conditions affecting your digestive system, guiding treatment decisions like medication or lifestyle changes.
Preparation for the Test
You’ll need to follow a specific diet and avoid certain foods or activities before the test to ensure accurate results. Your doctor will provide detailed instructions, often including fasting for a portion of the day.
What to Expect During the Test
The test is generally painless but may cause mild discomfort as the tube is inserted. You’ll wear a small device on your waist to record the pH sensor data while you sleep and go about your daily routine.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
Results from this test help diagnose conditions like GERD, Barrett’s esophagus, or other esophageal disorders. Abnormal findings may indicate the need for further testing, such as an upper endoscopy, or adjustments to your treatment plan, including medication or dietary modifications.
Frequently asked questions
How long does the test take?
Will I feel any pain or discomfort during the test?
Can I eat or drink normally during 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