Home Tests 24-hour pH monitoring
Test · Motility and function lab
24-hour pH monitoring
A 24-hour pH study measures how often and for how long stomach contents flow back into the food pipe over a full day and night. It is the most direct test for reflux. A fine tube is passed through the nose and connected to a small recorder that you wear home. You eat, work and sleep as usual.
At a glance
What it measures
Acid, and with impedance sensors, non-acid reflux, reaching the food pipe over 24 hours.
Time taken
20 minutes to place; you return the next day to have it removed.
Preparation
A four-to-six-hour fast. Acid-blockers are usually stopped a week before.
Results
A written report within a few days, explained at your follow-up.
What is a 24-hour pH study?
A soft tube about two millimetres thick carries sensors that detect acid. Its tip is positioned just above the valve at the lower end of the food pipe. The tube is taped at the nose and attached to a recorder worn on a belt or shoulder strap.
Tubes with additional impedance sensors also detect the movement of fluid and gas, so they pick up reflux that is not acidic.
The recorder has buttons that you press when you have a symptom, when you eat, and when you lie down. The report then shows whether your symptoms occur at the same time as reflux.
When do I advise it?
Reflux symptoms with a normal endoscopy
In most people with reflux the endoscopy is normal. The pH study shows whether reflux is truly present.
Before anti-reflux surgery
The operation helps only when reflux has been proved. See anti-reflux surgery.
Symptoms that continue on acid-blockers
To find out whether reflux is still occurring despite treatment, or whether something else is causing the symptoms.
Cough, throat symptoms or chest pain
When reflux is suspected as the cause and other reasons have been checked.
How do I prepare?
- Food and drink: nothing by mouth for four to six hours before the tube is placed.
- Acid-blockers: when the purpose is to prove reflux, they are stopped about seven days before the test, and antacids on the day before. When the purpose is to see why treatment is not working, they are continued. Your instruction sheet states which applies to you.
- Other medicines: take them as usual unless told otherwise.
- Clothing: wear a shirt or top that opens at the front.
What happens during the test?
Placing the tube
Oesophageal manometry is usually done first, at the same visit, to locate the lower valve. The pH tube is then passed through a numbed nostril and taped in place. You feel it at the back of the throat at first; this eases within an hour.
The 24 hours
Go home and live a normal day. Eat your usual meals at your usual times, including foods that normally trigger symptoms. Work, walk and sleep as you normally do. The result is useful only if the day is typical.
- Press the buttons for symptoms, meals and lying down
- Keep the short diary you are given
- Do not bathe or shower, as the recorder must stay dry
- Avoid sipping drinks continuously between meals
Removing the tube
You return the next day. The tube is removed in a few seconds and the recording is downloaded.
Afterwards and results
You can return to normal life and restart your medicines immediately. The report gives:
- Acid exposure time: the percentage of the 24 hours during which the food pipe was acidic. Under 4 percent is normal, and over 6 percent confirms reflux disease.
- The number of reflux episodes, by day and by night
- Symptom association: whether your symptoms coincided with reflux
What happens after the result?
| Result | What it means |
|---|---|
| Reflux confirmed | Treatment for reflux is justified, including surgery where it is suitable. |
| Normal acid, symptoms linked to reflux episodes | The food pipe is over-sensitive. Treatment aims at sensitivity. |
| Normal acid, no link with symptoms | Reflux is not the cause. Acid-blockers can be stopped, and attention turns elsewhere. |
What are the risks?
The test is low-risk. A sore nose or throat and a runny nose are common while the tube is in place.
Questions patients ask me about the pH study
Can I eat normally with the tube in place?
Yes, and you should. Eat regular meals, including foods that usually bring on symptoms. Swallowing feels slightly different for the first few bites.
Can I go to work?
Yes. The tube is visible at the nose, which some people find awkward, but normal activity gives the most useful recording.
Do I have to stop my acid medicine?
Usually, for seven days, if the aim is to prove reflux. If the aim is to check why treatment is not working, you continue it. Follow the written instructions for your test.
Is it uncomfortable?
You are aware of the tube in the throat for the first hour or so. Most people then get used to it and sleep normally.
What if the test is normal?
That is a useful answer. It means acid reflux is not driving your symptoms, and it spares you long-term medicine or an operation that would not help.
Sources
This page is written for patients and is based on the guidelines and studies below. It is for education and does not replace a consultation.
- Lyon Consensus 2.0 on the diagnosis of reflux disease. Gyawali CP et al. Gut. 2024. doi:10.1136/gutjnl-2023-330616
- American College of Gastroenterology guideline on gastro-oesophageal reflux disease. Katz PO et al. Am J Gastroenterol. 2022. doi:10.14309/ajg.0000000000001538