Version July 2025
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What is pH monitoring? —
This is a test to measure how much acid is in the esophagus (figure 1). The esophagus is the tube that carries food from the mouth to the stomach.
There is normally acid in the stomach to help with digestion. When acid backs up into the esophagus, it is called "acid reflux." The "pH" of a substance is a measurement of how acidic it is.
Sometimes, the doctor might also do a test called "impedance." This can be used to measure any fluid and gas that goes into the esophagus from the stomach.
Why might I get pH monitoring? —
Your doctor might order this test:
●To figure out if you have gastroesophageal reflux disease, or "GERD" – This is when stomach acid backs up into the esophagus and causes symptoms or damage. If your doctor is not sure if you have GERD or another problem, this test can help them figure out what is causing your symptoms.
●To check if your GERD treatment is working – If you are taking medicine for GERD but still have symptoms, this test can help them figure out the cause.
How do I prepare for pH monitoring? —
The doctor, nurse, or technician will tell you if you need to do anything special to prepare. You will need to avoid eating or drinking for 4 to 6 hours before the test. Some people need to stop taking certain medicines for a time before the test. If you were told to keep taking your medicines, you can take them with small sips of water.
What happens during pH monitoring? —
The test involves putting a small tube, called a "catheter," into your nose and down your throat.
During this test:
●The doctor, nurse, or technician will put the catheter through your nose and down your throat. They might put numbing gel in your nostrils first. They might have you take sips of water to help you swallow the tube.
●Once the catheter is in your esophagus, the other end will be attached to a small device. The device can be worn around the waist or over the shoulder.
●To keep the tube in place, the staff will tape parts of it to your face. This also prevents the tube from getting in the way during your daily activities like eating.
●The doctor, nurse, or technician will give you a diary to record your symptoms. They will tell you what to write in the diary.
●The catheter will usually stay in place for 24 hours.
●Most of the time, you can eat your normal diet while the catheter is in. In fact, doctors often recommend eating or other activities that tend to give you symptoms. This can help them learn more about your symptoms.
●The catheter needs to be removed by the medical staff. When it is time to remove the catheter, they will gently pull it out through your nose.
Most of the time, the test does not cause problems. While the catheter is being put in or removed, you might have some mild irritation in your nose and throat. Sometimes, this can make people gag or get a nosebleed.
What should I record in the diary? —
The staff will tell you exactly what to record. This might include recording the times you:
●Eat or drink
●Lie down
●Take certain medicines, such as medicine to reduce or block stomach acid
●Have certain symptoms, such as heartburn (a burning feeling in the chest) or chest pain
Most devices have buttons you can press when you have certain symptoms. You will get instructions about this, if needed. For example, you might be asked to press a button when you get heartburn.
Bring your diary to your follow-up appointment.
What do my results mean? —
The staff will tell you when to expect your results, and will contact you with the results. Or if you use an online "patient portal," you might get an alert there when your results are ready.
If your pH monitoring shows any abnormal results, your doctor or nurse will talk to you about what to do next. They might need to do more tests to figure out the cause.
If you have a health problem, your doctor will work with you to come up with a treatment plan.
Patient education: Acid reflux and GERD in adults (The Basics)
Patient education: Acid reflux and GERD in children and teens (The Basics)
Patient education: Gastroesophageal reflux disease in adults (Beyond the Basics)
Patient education: Gastroesophageal reflux disease in children and adolescents (Beyond the Basics)
