How to measure blood oxygen level?

Pulse oximetry is a way to measure how much oxygen your blood is carrying. By using a small device called a pulse oximeter, your blood oxygen level can be checked without needing to be stuck with a needle. The blood oxygen level measured with an oximeter is called your oxygen saturation level (abbreviated O2sat or SaO2).

This is a percentage of how much oxygen your blood is carrying compared to the maximum it is capable of carrying. Normally, more than 89% of your red blood should be carrying oxygen.

How to measure blood oxygen level
How to measure blood oxygen level

How to check oxygen level at home?

Why is it important to have my blood oxygen level checked?

If you have a lung disease, your blood oxygen level may be lower than normal. This is important to know because when your oxygen level is low, the cells in your body can have a hard time working properly.

Oxygen is the “gas” that makes your body “go,” and if you are low on “gas,” your body does not run smoothly. Having a very low blood oxygen level also can put a strain on your heart and brain.

Most people need an oxygen saturation level of at least 89% to keep their cells healthy. Having an oxygen level lower than this for a short time is not believed to cause damage.

However, your cells can be strained or damaged if low oxygen levels happen many times. If your oxygen level is low on room air, you may be asked to use supplemental (extra)oxygen.

The oximeter can be used to help see how much oxygen you need and when you may need it. For example, some people need more oxygen when asleep than when awake. Some need more oxygen with activity than when at rest.

How does a pulse oximeter work?

A pulse oximeter comes either as a small unit with a built-in finger/toe clip, or a small handheld device that has a wire probe that can attach or be applied to your finger, toe, or earlobe. The small unit is less expensive and more practical for home use.

Beams of light from the device pass through the blood in your finger (earlobe or toe) to measure your oxygen.

You will not feel this happen. The beams of light are “read” to calculate the percentage of your blood that is carrying oxygen. It also provides a reading of your heart rate (pulse).

To make sure the oximeter is giving you a good reading, count your pulse for one minute and compare the number you get to the pulse number on the oximeter. If they are the same, you are getting a good signal.

Should I get a pulse oximeter?

Most people do not need a pulse oximeter. Some people have prescribed a pulse oximeter if they have or could have periods of low oxygen; for example, when you are exercising or if you travel to high altitude.

Having a pulse oximeter in these cases will allow you to monitor your blood oxygen level and know when you need to increase your supplemental oxygen flow rate. Ask your health care provider what oxygen saturation number(s) they want you to maintain.

Pulse oximeters are available online or by prescription from your local pharmacy or medical supply company. In some cases, your insurance company will cover the cost of a pulse oximeter.

Cause of discrepancy between pulse oximetry and arterial blood gas

What is the difference between the oxygen information reported from an oximeter versus from an arterial blood gas?

An oximeter indirectly measures the amount of oxygen that is carried by your blood. An arterial blood gas (ABG) directly measures both the amount of oxygen carried by your blood and the actual amount of gases (oxygen and carbon dioxide) that are in your blood. To get an ABG, blood is taken directly out of your artery (usually from the
wrist) and can be painful. Oximetry is painless but is not as accurate as an ABG. Also, a pulse oximeter does not measure your carbon dioxide level.

How accurate is the pulse oximeter?

The oxygen level from a pulse oximeter is reasonably accurate. Most oximeters give a reading 2% over or 2% under what your saturation would be if obtained by an arterial blood gas.

For example, if your oxygen saturation reads 92% on the pulse oximeter, it may be actually anywhere from 90 to 94%. The oximeter reading may be less accurate if a person is wearing nail polish, nail polish only affects readings if the sensor is placed over the polish. See that the sensor is at the base of the nail.

If artificial nails are too long, may need to clip the nail shorter, trying putting the probe on sideways, or try using a toe instead. A pulse oximeter may also be less accurate with very low oxygen saturation levels (below 80%) or with very dark skin.

When should I use a pulse oximeter?

If you have been prescribed an oximeter by your health care provider, ask them when they want you to use the oximeter to monitor your blood oxygen level. Ask your health care provider when you should change the flow rate on your supplemental oxygen and at what reading you should seek medical attention.

When using an oximeter what is a normal reading?

Times, when an oximeter reading may be helpful, are:

  • When you are first prescribed oxygen. This helps your health care provider know if and how your oxygen saturation levels change when doing activities at home.
  • During or just after exercising. Your body, like your car, needs more oxygen (“gas”) when you are moving. Your oxygen saturation might be checked during activity to see if you have low oxygen that might not be an issue at rest. Your health care provider will decide with you what to do if you have oxygen problems with exercise.
  • If you are flying or traveling to a high altitude location, your supplemental oxygen needs may increase during these times.

what are the 2 readings on a pulse oximeter?

  • oxygen saturation
  • pulse rate

How can I get the best reading from my pulse oximeter?

Your pulse oximeter measures your oxygen saturation or percentage of blood carrying oxygen.

To get the best reading from your oximeter, you need to make sure enough blood is flowing to the hand and finger wearing the device. The best reading, therefore, is achieved when your hand is warm, relaxed, and held below the level of your heart.

If you smoke, unfortunately, the reading on your oximeter may be higher than your actual oxygen saturation. This is because smoking increases carbon monoxide levels in your blood, and the oximeter cannot tell the difference between the gas carbon monoxide from oxygen.

If you smoke, talk to your health care provider about how to properly read your oximeter numbers.

In addition to the inaccurate readings described above, sometimes you can get abnormal readings from your oximeter because the probe of the oximeter is not functioning properly. You can bring your oximeter to your health care provider’s office or equipment company to have it checked against theirs for accuracy.

How can I check my oxygen level at home?

Using a Finger Pulse Oximeter, which is a small device that is attached to your finger to measure the amount of oxygen in the blood travelling round your body. The Oximeter takes an SpO2 reading – an estimation of the amount of oxygen in your blood.

More on this story

Pulse Oximeters: Answering Your Frequently Asked Questions

How to check Oxygen level without Oximeter

How to check oxygen level without oximeter?

The app uses “reflective pulse oximetry,” which allows the light source and sensor (the camera in this case) to be next to each other.

Pulse Oximeter accuracy comparison

Pulse Oximeter accuracy comparison

Pulse oximetry is so widely prevalent in medical care that it is often regarded as a fifth vital sign. It is important to understand how the technology functions as well as its limitations because erroneous readings can lead to unnecessary testing.

Fingertip Pulse Oximeters

Pulse Oximeters

  • What is the best pulse oximeter?
  • What is a normal oxygen saturation level?
  • Are any oximeters made in the USA?
  • Pulse oximeters FDA approved and more…