24-Hour Probe Study

March 22, 2017

24-Hour Probe Study

What is a 24-hour probe study?

The 24-hour probe study measures the pH (acid level) in your food pipe (esophagus).

Your esophagus is the tube that goes from your mouth to your stomach. If you have gastroesophageal reflux disease (GERD), the pH levels in your esophagus can be too high. GERD causes stomach acids to flow back into your esophagus. This can cause heartburn.

For the 24-hour probe study, your health care provider will insert a thin tube into your nose. The tube goes down into your esophagus. The tube will have either 1 or 2 sensors on it. The sensors read your pH levels.

Once the tube is in place, you can go home. You will keep the tube in for 1 day. But you will be able to do most of your normal activities while you have the tube.

After 24 hours your health care provider will remove the tube and sensors. Your doctor will check the information to see if you have GERD.

Why might I need a 24-hour probe study?

The 24-hour probe study is used to see if you have GERD. It may also be used to see if your GERD treatment is helping to reduce your stomach acid level.

If GERD isn’t treated, the acids can hurt the tissues of your esophagus. This can lead to more health problems, such as Barrett's esophagus. That is when abnormal tissues grow and take over normal esophagus tissue.

The 24-hour probe study can help stop such problems. It can tell if you have any medical problems. It can also make sure the care you are getting is working.

What are the risks of a 24-hour probe study?

The 24-hour probe study has no real risks. There are only a few small side effects. It may not feel very good when your doctor inserts the tube and when you wear it. When the tube is inserted, you may feel:

  • Mild pain when swallowing
  • Mild pain in your throat
  • Pain in your chest

How do I get ready for a 24-hour probe study?

Your doctor will explain how the 24-hour probe study is done. Be sure to ask any questions you may have.

You will be asked to sign a consent form that gives your permission to do the test. Read the form carefully and ask questions if something is not clear.

Tell your health care provider about all the medicines you take. This includes over-the-counter medicines such as ibuprofen. It also includes vitamins, herbs, and other supplements.

You must not eat or drink anything for 8 hours before the test. This often means no food or drink after midnight.

Tell your health care provider if you:

  • Are pregnant or think you may be pregnant.
  • Are sensitive to or are allergic to any medicines, iodine, latex, tape, or anesthesia drugs (local and general).
  • Have a history of bleeding disorders or are taking any blood-thinning (anticoagulant) medicines, aspirin, or other medicines that affect blood clotting. You may have to stop taking these medicines before your surgery.

Your health care provider may have other instructions for you based on your medical condition.

What happens during a 24-hour probe study?

The inside of your nose will be numbed. This will make you more comfortable as the tube and sensor are inserted. Your health care provider will then put the tube (with 1 or 2 sensors on it) into your nose. He or she will push the tube down your throat while you swallow.

The sensor will stay just above the lower esophageal sphincter (LES). The LES is the muscle that keeps stomach acids out and lets food into your stomach. The LES is at the bottom of your esophagus. You may have other sensors too. They may check the pH levels in your stomach and esophagus.

A small recorder will be on the end of the tube that comes out of your nose. It will be joined to a strap placed over your shoulder.

Once the tube is in place and you are wearing the strap, you can go home. You will have to wear this for 24 hours. But you should be able to do most of your normal activities during the 24-hour probe study.

Your doctor will likely have you keep a diary. You should list all the foods you eat and when you eat them. You should also list when you sleep and any symptoms you have. Follow your doctor’s instructions very closely. This will help you get the most exact results.

What happens after a 24-hour probe study?

After 24 hours you will go back to your health care provider. He or she will take out the tube and any sensors. Your health care provider will check the results and compare them with your diary. He or she will score the results. The results will show if acid levels in your esophagus are too high.

Your health care provider will then make a care plan for you. He or she may change the plan you have.

Your new care plan will:

  • Help lower your stomach acid level.
  • Keep your symptoms under control.
  • Stop stomach acid from hurting your esophagus.

Next steps

Before you agree to the test or the procedure make sure you know:
  • The name of the test or procedure
  • The reason you are having the test or procedure
  • The risks and benefits of the test or procedure
  • When and where you are to have the test or procedure and who will do it
  • When and how will you get the results
  • How much will you have to pay for the test or procedure


March 22, 2017


Hirano, I., Esophageal Reflex Testing Guidelines, American Journal of Gastroenterology (2007); 102; pp. 668-685

Reviewed By:  

Berry, Judith, PhD, APRN,Foster, Sara, RN, MPH