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24-hour pH monitoring


24-hour pH monitoring (also known as an oesophageal acidity test) measures the levels and any changes in the levels of stomach acid in the oesophagus over a 24-hour period. The test is often used in conjunction with high resolution oesophageal manometry to diagnose Gastro-Oesophageal Reflux Disease (GORD) and to monitor the effectiveness of any medication prescribed to help with the condition.

The test is also often used to determine the cause of excessive crying in young infants.


Your practitioner may recommend the test if they suspect a possible diagnosis of any of the following conditions...

  • Barrett's Oesophagus.
  • Dysphagia.
  • Scarring of the oesophagus.
  • Gastroesophageal reflux disease (GORD).
  • Reflux / heartburn.

Further tests may be required if the pH test indicates elevated acid levels.

Preoperative Instructions

Patients will need to stop eating and drinking at midnight on the night before the test. It is also strongly advisable not to smoke on the day of the test and to avoid alcohol.

Some medications interfere with the test and so you may be asked to suspend these medications for a period before the test. This is typically 24 hours, but some medications may need to be halted two weeks or more before the test. The types of medication that may need to be stopped include...

  • Alpha blockers.
  • Antacids.
  • Anticholinergics.
  • Cholinergics.
  • Corticosteroids.
  • H2 blockers.
  • Proton pump inhibitors.

Do not stop taking any prescribed medications until advised to do so by your doctor or other medical professional.


The test involves passing a small tube into the oesophagus via the nose. The tube is then connected to a recording device that is normally attached to the belt for the 24-hour period. At the same time the patient must keep a food and drink diary and record information about their sleep pattern and times of any symptoms during the period.

Infants and young children undergoing the test may need to remain in the hospital for the whole duration.

During the insertion of the tube, patients may experience some gagging or discomfort as it passes into the throat. It is also not uncommon to have a minor nosebleed or a sore throat or blocked nose afterwards.