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Peninsula Gastroenterology Medical Group, Gastroenterologists
Redwood City: 2900 Whipple Ave | Suite 245 |Redwood City, CA 94062 • Phone: 650-365-3700
Mountain View: 2495 Hospital Drive | Suite 600 | Mountain View, CA 94040 • Phone: 650-964-3636

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Ambulatory 48 Hour pH Test

Patient Procedure Instructions


To record the amount of severity of reflux into the esophagus.

Preparation for the Study

Ten Days Prior to the Study

Unless otherwise directed by the doctor, stop taking the following medications:

  • Aciphex
  • Nexium
  • Prevacid
  • Prilosec
  • Protonix

The Day of the Study

  1. If your procedure is in the morning do not eat or dink anything after midnight the night prior to your procedure:
  2. If your procedure is in the afternoon, you may have clear liquids up to 8am (coffee, tea, soda, water, clear juices, clear broth, popsicles and jello).
  3. Be prepared to be at the center for one hour. Typically this procedure is done in conjuction with an Endoscopy, so you will need to have a ride home.
  4. The pH study will last for 48 hours.
  5. Do not take antacids the day of the study without your doctors approval (Tums, Rolaids, Mylanta, Maalox). If you do not take an antacid be sure to document it on your diary.

48 Hours Later

You will need to return to the Atherton Endoscopy Center 48 hours later to drop off your receiver.

Related Links

Atherton Endoscopy Center photo

Atherton Endoscopy Center

While you are a patient at Atherton Endoscopy Center, our highly competent and professional staff will care for you. Everyone from the receptionist to the physician embraces our philosophy of patient-focused care. Above all, our staff is friendly and concerned for your comfort.