Esophageal pH measurement (24-hour ambulatory monitoring)
This test measures how acidic or basic the acid in your stomach is while you sleep and throughout the day. It helps doctors check if stomach acid is flowing back into your esophagus too often, which can cause heartburn or acid reflux.
["This test helps diagnose and monitor conditions like GERD (acid reflux) and gastroesophageal reflux disease (GERD)."]
Key facts at a glance
- LOINC
- 57823-7
- Short code
- PT Esophagus W RNC IV
- Synonyms
- PT Esophagus W RNC IV
- Category
- chemistry
- Sample
- serum
- Container
- Red-top tube (SST)
- Units
- N/A
- Ref low
- 0.8
- Ref high
- 1.2
- Critical range
- — – 5 N/A
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 18–65 years
- Method
- pt
- CPT
- 85610
- SNOMED
- 396252006
- 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
How the Test Works
A small tube called a pH sensor is placed in your esophagus during a short procedure. The sensor is connected to a small recording device worn on your belt. As you go about your normal activities, the device records pH levels in your stomach over 24 hours.
Preparation
No special preparation is needed for this test. You may eat and drink normally, but avoid taking any medications that could affect stomach acid (like certain antacids or heartburn medications) unless approved by your doctor. You’ll need to wear the recording device for a full day.
What to Expect During the Procedure
The procedure takes about 15 minutes. A doctor or nurse will insert the sensor through your nose into your esophagus. You may feel a slight discomfort or pressure, but it’s usually not painful. The sensor is then attached to the recording device, and you’ll be able to go home the same day.
Aftercare
After the test, you can return to your normal activities. Remove the recording device when you go to bed and return it to your doctor. Avoid removing the sensor yourself. If you experience any unusual symptoms like difficulty swallowing or severe pain, contact your doctor immediately.
Reference range
INR: 0.8-1.2 (warfarin: 2.0-3.0)N/A
Inform your healthcare provider if you are taking blood thinners. No special preparation required.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
This test is crucial for diagnosing conditions like GERD, where stomach acid frequently flows back into the esophagus. It can also help determine if you have Barrett’s esophagus (a precancerous change in the lining of the esophagus) or other complications. Results help guide treatment plans, such as lifestyle changes, medications, or in severe cases, surgery.
Frequently asked questions
Why would my doctor recommend this test?
What are the possible risks or side effects?
How long will I need to wear the recording device?
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