How to use a pulse oximeter

Track your oxygen level and pulse with this simple tool. 


What is a pulse oximeter?

A pulse oximeter is a small, easy-to-use tool about a few inches long. You can use it to measure the oxygen in your blood.

How does a pulse oximeter work?

Most pulse oximeters clip on your finger. It shines a beam of light that passes through your skin and bounces back. It then “reads” that light to figure out how much oxygen is in your blood. It will also tell you your pulse (heart rate).


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Why does a blood oxygen level matter?

Your body needs oxygen to live. When you breathe, your lungs pull oxygen from the air into your blood. Then your blood carries that oxygen to every cell in your body. You need a certain level of oxygen to be healthy.

What do the numbers mean?

  • On a pulse oximeter, the normal oxygen range is 95% to 100%. Anything under 90% is low. If you have a low oxygen level for too long, it can be hard on your heart and brain.
  • People who can’t get enough oxygen on their own may need extra oxygen. Their doctors will have them use special equipment to give them oxygen through a mask or tubes through their nose. The pulse oximeter can help your doctor learn if the extra oxygen is working.

When should I check my oxygen level?

Here are some examples of when people usually use a pulse oximeter:

  • If you start using oxygen at home, your doctor may want you to check your oxygen levels.
  • You may use one while exercising or after exercising to see if you need more oxygen when you’re moving.
  • If you fly or travel to a high-altitude place (more than 8,000 feet above sea level), you may use one. The air has less oxygen at high altitudes. This can cause some people to get sick.

How do I use a pulse oximeter?

Most pulse oximeters come with directions. But here are the basic steps:

  • Remove the pulse oximeter from the box and put in the batteries.
  • Clip the pulse oximeter on your index (pointer), middle or ring finger.
  • Press the button on your pulse oximeter to start it. Keep your hand still.
  • Write down:
    • The date
    • Your blood oxygen level
    • Your pulse
    • How much you've been moving

How do I get the best results?

To get the best results with a pulse oximeter:

  • Relax.
  • Make sure your hand is warm.
  • Hold your hand below the level of your heart.

You may get a poor reading if you have:

  • Cold hands
  • Poor blood circulation (your blood isn’t reaching all the parts of your body)
  • Darker skin
  • Thick skin
  • Dark fingernail polish, or long or artificial nails

You may also get poor results if you smoke or use tobacco.

How does this tool help check for COVID-19?

Some people have used pulse oximeters to check their oxygen levels when they think they have COVID-19. If you think you have COVID-19, call your doctor.

You can also check with the Centers for Disease Control and Prevention (CDC). The CDC has the most up-to-date list of symptoms and directions for testing and getting care.

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The information provided is for general informational purposes only and is not intended to be medical advice or a substitute for professional health care. You should consult an appropriate health care professional for your specific needs.