Gastric pH (Esophageal Ambient pH)
This test measures the acidity level in your stomach using a small sensor placed in your esophagus to monitor pH over time.
["Understanding your stomach’s acidity can help diagnose conditions like acid reflux or GERD."]
Key facts at a glance
- LOINC
- 104833-9
- Short code
- Skin IgA SerPl Ql Monkey esoph
- Synonyms
- Skin IgA SerPl Ql Monkey esoph
- Category
- chemistry
- Sample
- serum
- Container
- Red-top tube (SST)
- Units
- N/A
- Ref low
- 7.35
- Ref high
- 7.45
- Critical range
- 7.2 N/A – 7.6 N/A
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 18–65 years
- Method
- monkey-esophagus-substrate
- CPT
- 82784
- 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
Why This Test Is Done
Your healthcare provider may recommend this test if you experience frequent heartburn, chest pain, trouble swallowing, or unexplained symptoms like nausea or vomiting. It helps determine whether your symptoms are linked to excess stomach acid or another issue.
How the Test Works
A thin, flexible tube with a small sensor is inserted through your nose into your esophagus. The sensor continuously records pH levels over a set period (often 24 hours) while you eat, drink, and go about your normal activities. The results help identify patterns of acid reflux or other abnormalities.
Preparation Before the Test
No special preparation is needed, but you may be asked to avoid certain medications (like antacids) that could affect results. Follow your provider’s instructions to ensure accurate readings.
What to Expect During the Test
You’ll likely feel mild discomfort or pressure when the tube is inserted, but it’s usually well-tolerated. You can eat and drink normally unless instructed otherwise. The sensor is removed after the test period, and you may experience mild nasal irritation afterward.
Reference range
NCBI: pH 7.35-7.45N/A
No special preparation usually required. Stay well hydrated. Inform your healthcare provider of all medications and supplements you are taking.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
Clinical Significance
Frequently asked questions
This test helps diagnose conditions like gastroesophageal reflux disease (GERD), Barrett’s esophagus, or other esophageal disorders by showing whether stomach acid is flowing back into the esophagus excessively. It also helps guide treatment decisions, such as medication adjustments or lifestyle changes.
A low pH reading indicates high stomach acid levels, which may suggest GERD or other acid-related issues. Your provider will interpret results in the context of your symptoms and other tests.
The test itself takes about 30 minutes to insert the sensor, but the actual monitoring period is typically 24 hours. The full process, including preparation and follow-up, may take a few days.
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 17, 2026. · Read our editorial policy