Preparing for 24-hour pH or impedance monitoring for reflux: what to log, why clinics differ on medicine, and what to ask
How to prepare for 24-hour pH or impedance monitoring for reflux: why clinics differ on medicine, how to keep the day log, and what to ask.
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For 24-hour pH or impedance monitoring you get a leaflet, a diary form and rules that vary by clinic. You can note the weeks before on paper or in the symptom diary in Sam. Its monthly report as a PDF shows your symptom days. To prepare, follow your clinic's written instructions on medicines and fasting. On the test day, log your body position, meals and symptoms, with times read only from the recorder.
This text does not replace your clinic's instruction. On medicines and fasting times, services differ and your clinic decides; the hours quoted in the FAQ are examples from two sources, not your instruction.
What does the test record, and why does the diary matter?
A thin tube runs through your nose into your esophagus. Johns Hopkins describes a small, flexible catheter that stays in place for 24 hours and sends data to a recorder you wear. A sensor measures when acid from the stomach reaches the esophagus. In some cases, impedance adds a record of reflux that is not acid.
The device records events, but only you know what you felt. So the diary is part of the test. MedlinePlus says you keep a diary of your symptoms and the food you eat during the 24 hours. Clinicians also mark your meals, because eating changes the reading.
The times matter. If your acid level is normal, the question becomes whether your symptoms line up with reflux events in time. Without your symptom times, that question stays open. That is exactly why the on-day log exists.
Why does every clinic differ on the medicine?
The main reason is the question being asked. Sometimes the test is meant to show whether acid gets through despite your medicine, and sometimes it is meant to show whether you have abnormal acid reflux at all, for example before surgery.
That is why one clinic may pause your acid-suppressant and another may keep you on it. Johns Hopkins says your doctor discusses your medicines and tells you if or when to stop any. For some services, an NHS leaflet asks you to stop certain acid and indigestion medicines days before. There is no universal rule, so the clinic that measures decides, and it gives you the plan in writing.
Who decides about pauses, and what must the clinic know?
The clinic or hospital that runs the test decides. Bring your whole medicine list: everything you take regularly, including anything over the counter. Never stop a prescribed medicine, including heart or blood-pressure tablets, without the clinic's written plan and your prescriber's agreement.
Your instruction comes in writing. If something is unclear, ask before the appointment, not on the day. The clinic's leaflet is the authority, not this text.
How do you fill in the test-day diary?
The clinic gives you its own form, and that one counts. You log your body position, your meals and your symptoms. Your form says which positions to mark; the NHS leaflet asks you to press the button when you lie down.
For a symptom such as heartburn or chest discomfort, note when it started and when it stopped. Read the times from the recorder only, and log the buttons you press on the device and when.
As a memory aid for the night before, not a replacement for the form:
| Field | What you enter | Source |
|---|---|---|
| Time | only from the recorder | clinic leaflet |
| Position | lying down, and any other change your form asks for | NHS |
| Meal | start and end | MedlinePlus, Johns Hopkins |
| Symptom | type, e.g. heartburn, start and end | Johns Hopkins |
| Device button | which one, when | NHS |
| Sleep | falling asleep and waking | clinic form |
| Unusual day | e.g. a skipped meal | your own note |
How do you eat, lie and move on the test day?
Most services ask for a normal day so the recording reflects your real life. Continue most of your usual activities. When you sleep, you take the belt off and place the recorder beside or under your pillow, says the NHS leaflet.
Food rules come from your clinic. For one NHS service, that means no chewing gum, no fizzy drinks and no acidic foods such as citrus during the recording. Do not shower or bathe, because water can damage the equipment. Different clinics have different lists, so follow your own.
What belongs with the doctor instead of a diary?
A diary and a log do not answer alarm features. These should be raised with a doctor, even if your appointment is weeks away:
- Trouble swallowing (dysphagia)
- Pain when swallowing
- Signs of bleeding, such as vomiting blood or black stools
- Unintentional weight loss
- Iron deficiency anaemia
- Repeated or persistent vomiting
NICE guideline CG184 sets out when adults with reflux or dyspepsia symptoms need further investigation. Your doctor decides whether an urgent endoscopy is needed.
Chest discomfort goes in your log, because you do not have to know where it comes from. But with severe chest pain or trouble breathing, do not wait for notes: call your local emergency number (112 in the EU, 999 in the UK, 911 in the US).
Which questions do you ask before the test?
Take these to the clinic or ask on the phone:
- Will I measure with or without my acid medicine, and why?
- Which of my medicines does the plan affect, and who checks with my prescriber?
- How many hours before should I stop eating?
- Is a manometry needed first to place the tube?
- Which buttons does the device have, and what are they for?
- Can I work and drive?
- What should I do if symptoms get strong, and who do I contact?
- When do I get the results, and who explains them?
The weeks before the test, only you can tell the clinic how often symptoms came and whether they woke you at night. The on-day log covers just 24 hours, which is why the weeks before belong in a diary. The GERD program in Sam holds heartburn days. Without a confirmed diagnosis, use the symptom diary instead. Reflux fits into meals, sleep and daily life in living with GERD: meals, sleep and daily life, and sleep by night in sleep, heartburn and GERD with Apple Health.
Log reflux days before the test and take a report to the appointment
You bring symptoms with dates instead of an impression from memory. The Reflux (GERD) program is a diary with a doctor report and a monthly questionnaire, and it starts after you switch on that a doctor has diagnosed reflux disease.
- Instead of remembering: heartburn days and nights with symptoms sit with their dates in your history, not as "sometimes more, sometimes less".
- Instead of paper: the doctor report as a PDF covers the period you choose, ready to show at the appointment.
- Instead of Apple Health alone: the program home also shows your sleep and weight from Apple Health in the same app.
On the test day you fill in the clinic's form. Sam does not replace it and reads no times from the recorder.
Try Sam HealthSam is a wellness companion, not a medical device. The app does not diagnose, treat, cure or prevent any condition or health state. Always consult qualified professionals for medical decisions.
Related reading
- Living with GERD: meals, sleep and daily life
- Sleep, heartburn and GERD with Apple Health
- Heartburn or gastritis? Spotting the difference
- Globus Sensation: Lump in Throat and Reflux
- Shift Work and Chronic Conditions: What to Record
Sources
Updated: October 2026
- MedlinePlus: Esophageal pH Test (last updated 10 September 2024)
- Johns Hopkins Medicine: 24-hour pH-Impedance Testing
- North Tees and Hartlepool NHS Foundation Trust: 24-hour pH monitoring study (reviewed 30 March 2026)
- NICE: Gastro-oesophageal reflux disease and dyspepsia in adults: investigation and management (CG184) (published 2014, updated 2019)
More on Reflux (GERD)
Frequently Asked Questions
How long does 24-hour pH monitoring last?+
A thin tube runs through your nose into your esophagus and connects to a recorder you wear for about 24 hours. MedlinePlus describes the test as measuring acid for 24 to 96 hours depending on the device. Your clinic explains your exact plan.
Do I have to stop my acid medicine before the test?+
There is no single answer, because it depends on the question being asked. Johns Hopkins says your doctor will discuss your medicines and tell you if or when to stop any before the test. Your clinic's written instruction is what counts, so you do not decide on your own.
How long do I fast before the test?+
This differs between services. Johns Hopkins says to stop eating and drinking about four hours before, and MedlinePlus says four to six hours. Your clinic gives you the hours for your appointment in writing. If they are not clear, ask before the day.
How precise does the diary have to be?+
Full detail helps. You aim to log your symptoms, meals and changes in position with their times from the recorder. Johns Hopkins says your doctor may ask you to keep a diary of meals, activities and any symptoms, so the readings can be matched to what you felt.
Can I lie down during the recording?+
Yes, and lying down belongs in your diary. The NHS leaflet asks you to press the button and log when you lie down, because position changes acid exposure. Your clinic tells you how to record position on its own form.
What can I eat on the test day?+
The NHS leaflet for one service says avoid chewing gum, fizzy drinks and acidic foods such as citrus through the day. Other services give different lists. Eat a normal day, but follow the food rules your own clinic gives you.
Which symptoms belong with the doctor, not in a diary?+
Trouble swallowing, pain when swallowing, signs of bleeding, unintentional weight loss and repeated vomiting are alarm features that a doctor should look into, rather than questions for your diary. With severe chest pain or trouble breathing, call your local emergency number (112 in the EU, 999 in the UK, 911 in the US).