Using a Pulse Oximeter


A pulse oximeter is a device that checks to see how much oxygen your blood is carrying.

Usually a small clip is put on the end of your finger. (Sometimes it's put on your toe or earlobe.) The device shines a light beam through the skin. It estimates your oxygen level by measuring the percentage of your blood that's carrying oxygen. Your oxygen level (or oxygen saturation, SpO2) shows on the display screen.

Pulse oximeters are used in doctors' offices and hospitals. Some people use one at home.

Why is it used?

A pulse oximeter is used at home to watch for changes in oxygen levels. Your doctor may suggest using one if you have a condition that affects your oxygen level. Your test results and changes in your symptoms are used together to check your health and make decisions.

How do you use a pulse oximeter?

Follow the instructions that come with your oximeter. Here are the steps:

  1. Turn it on.
  2. Sit quietly for a few minutes.
  3. Be sure your hand is warm.
  4. Clip the device on the end of a finger. Use a finger that doesn't have nail polish or an artificial nail.
  5. Keep your nail facing up.
  6. Hold your finger still and below the level of your heart.
  7. You'll see results in a few seconds. Wait until you see one steady number for the oxygen level.

Your doctor can help you know what numbers are normal for you.

Ask your doctor how often to check your oxygen level. Your doctor may suggest checking it at different times, during exercise, or anytime your symptoms get worse. Keep a record of your levels, and watch for changes. Watch for new or worse symptoms. Your doctor can tell you what to do if you notice your levels are getting lower.

What affects the results?

Many things can affect your results from a pulse oximeter. These include darker skin colors, skin thickness, tobacco use, and poor blood flow in your finger. The device also may not show accurate results if you have cold hands or if you wear nail polish or artificial nails.

If you have a darker skin color, a pulse oximeter may miss low oxygen levels. You may not know that your levels are low and that you need medical care. So it's important to watch for symptoms along with changes in your oxygen levels. Talk with your doctor about symptoms you may have with low oxygen levels. These symptoms include fatigue, weakness, and shortness of breath.

The U.S. Food and Drug Administration (FDA) does not regulate over-the-counter pulse oximeters the same way it regulates oximeters that are prescribed or used by doctors. An over-the-counter pulse oximeter can be sold without research on how well it works.

When should you call for help?

Your doctor probably told you what numbers to watch for when you use your pulse oximeter. If not, here is some guidance.

Call your doctor if:

  • Your blood oxygen level (SpO2) drops below 95%. This is true even if the number only drops when you're active.

If you have certain health problems, like COPD, your oxygen level may always be lower than 95%. Ask your doctor what oxygen number you should expect when using your pulse oximeter. Find out which number is a sign that you should call for help.

Watch closely for changes in your health, and be sure to contact your doctor if:

  • Your oxygen level is getting lower over time.
  • You are worried about your levels.
  • You have new symptoms or your symptoms get worse.
  • You are not getting better as expected.


Current as of: August 6, 2023

Author: Healthwise Staff
Clinical Review Board
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