A Guide to Pulse Oximeters


If you have or are concerned about having an illness or condition that affects your body’s oxygen levels, you may be considering using a pulse oximeter. This guide will walk you through what a pulse oximeter is and how to best use one.  

Pulse Oximeter

What is a Pulse Oximeter?

A pulse oximeter, sometimes referred to as a pulse ox, is a small, portable device that measures the oxygen saturation level of your blood. This measurement is displayed as a percentage comparing the amount of oxygen in your blood to the maximum amount of oxygen your blood is capable of carrying. Often, the pulse oximeter will also display your heart rate. 

How does it work?

Pulse oximeters typically have a clip-like design that allows you to attach them to your finger, toe, or earlobe. Rather than pricking your body part with a needle, pulse oximeters use beams of light that painlessly pass through the blood in that area to measure your blood oxygen levels.

The amount of light absorbed by the blood varies depending on how oxygenated the blood is. So, according to the American Lung Association, a pulse oximeter determines the percentage of oxygen in the blood by shining light through the body part it’s attached to and analyzes the amount of light that passes through the blood.  

What is a pulse oximeter?

What are Pulse Oximeters Used for?

The blood oxygen level measurement that a pulse oximeter provides indicates how well the heart is pumping oxygen throughout the body. For this reason, pulse oximeters are most often used in hospital settings. They can quickly alert doctors of low oxygen levels in patients, especially newborns and patients under anesthesia, and help doctors assess if a patient needs or responds well to supplemental oxygen.

However, pulse oximeters can also be used at home to monitor and provide peace of mind for anyone with a condition that may cause them to experience periods of low oxygen levels.

According to Healthline, these conditions may include:  

  • Asthma
  • Anemia
  • Chronic Obstructive Pulmonary Disease (COPD)
  • Pneumonia
  • Lung cancer
  • Heart attack or heart failure
  • Congenital heart defects

A doctor might also prescribe a pulse oximeter to people with these conditions to monitor oxygen levels while exercising, traveling at high altitudes, taking a new medication, or starting out on prescribed supplemental oxygen. 

Pulse oximeters and COVID-19

In addition to monitoring those with chronic lung and cardiovascular conditions, pulse oximeters could help detect the novel coronavirus, or COVID-19. According to Everyday Health, COVID-19 patients have sometimes had dangerously low blood oxygen levels without experiencing shortness of breath. Using a pulse oximeter could alert you to this drop in blood oxygen levels before it becomes severe.

That said, a pulse oximeter is not a replacement for a consultation with a trained health professional, and a low saturation of oxygen in the blood is not the only symptom of COVID-19. If you use a pulse oximeter, continue to be conscious of other possible coronavirus symptoms. Consult your doctor if you experience these symptoms, even if the device shows healthy blood oxygen levels.  

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

Low blood oxygen levels make it harder for your body to pump oxygen to your cells and tissues. According to the American Thoracic Society, having low blood oxygen levels for a short time is not known to be harmful, but experiencing low levels often can damage your cells and tissues. This damage can cause a decline in your bodily functions and put a strain on your heart and brain.

If you have a condition that can cause low blood oxygen levels, it’s important to have your levels checked regularly. It may also be important to check your levels if you experience symptoms of low oxygen, such as wheezing or chest pain, when sleeping, exercising, or traveling at high altitudes. With this knowledge, you can receive supplemental oxygen or other medical care when needed to prevent cell and tissue damage.  

Are Pulse Oximeters Safe?

Yes, pulse oximeters are non-invasive and generally considered safe to use. You may experience minor skin irritation, such as redness or sensitivity, but otherwise, there are no known health risks to using this device when it is used correctly. 

Pulse oximeter misuses

Most health risks posed by the device occur when the pulse oximeter is used incorrectly. For example, if it is fitted too tightly or worn for prolonged periods, it can decrease blood flow to the body part it’s attached to. Often, this causes minor, temporary numbness or skin discoloration, but the tourniquet-like effect can increase the risk of a burn injury.

The main risk of using a pulse oximeter incorrectly is receiving an incorrect reading, which can be harmful if your true oxygen levels require medical attention. There are many factors that can influence a reading, including the fit and positioning of the device. We will go through how to correctly use a pulse oximeter and get the best possible reading in the “How to use a pulse oximeter” section of this guide.

However, it is also important to understand the limitations of pulse oximetry. One way someone may “misuse” a pulse oximeter is by believing a healthy reading indicates a clean bill of health, when that’s not always the case. Pulse oximeters do not evaluate your ability to ventilate or whether the oxygen in the blood is available for tissue or cellular use, and factors out of your control such as hemoglobin levels and arterial pulse might be affecting the reading.

A pulse oximeter is not a substitute for other forms of monitoring. If you experience difficulty breathing, shortness of breath, or dizziness, it’s best to seek medical attention even if your pulse oximeter shows a healthy reading.  

How to Use a Pulse Oximeter

To use a pulse oximeter:  

  • Clip the device to a part of your body, such as your finger, toe, or earlobe. If it is hard to clip on a certain body part, such as your big toe, don’t force it. Most at-home pulse oximeters work best when used on your index finger.
  • Ensure that the device is evenly positioned and fits securely. You don’t want it too tight, as it might cut off circulation, but if it’s too loose, it might fall off or affect the reading.
  • Ensure that the device is evenly positioned and fits securely. You don’t want it too tight, as it might cut off circulation, but if it’s too loose, it might fall off or affect the reading.
  • Within a few seconds, the pulse oximeter should display your current oxygen saturation level and heart rate.

You might use a pulse oximeter only for a quick reading, in which case you will remove the device after these measurements are recorded. However, you can also keep the device on to monitor your blood oxygen level and heart rate for certain periods of time, such as during physical activity or while sleeping.

How to Read a Pulse Oximeter

Most pulse oximeters will display two numbers: your blood oxygen level and your heart rate. Typically, the blood oxygen level will be indicated by SpO2 and the heart rate will be indicated by PR BPM or HR.

Your blood oxygen level will be displayed as a number between 0 and 100. This is because the device measures it as the percentage of oxygen in the blood compared to the amount of oxygen your blood is capable of carrying.

If the device is used correctly and the reading is not influenced by other factors, your SpO2 reading will be accurate within a 2 percent difference. For example, if the oximeter displays a blood oxygen level of 92, your true blood oxygen level is between 90 and 94. 

Understanding Your Reading

According to Healthline, an SpO2 reading of 95 or higher is typically considered normal. However, if you have a condition such as asthma or COPD, your “normal” reading may be slightly lower. If you’re considering using a pulse oximeter to monitor your condition, be sure to consult your doctor about what “normal” looks like for you.

A reading of 92 or lower may indicate that you are experiencing hypoxemia, or below-normal levels of oxygen in the blood. More than 89 percent of your blood should be carrying oxygen for your cells or tissues to receive an adequate supply.

The oxygen saturation of your blood might drop for a number of reasons, including insufficient oxygen in the air you breathe, hyperventilation, inhalation of poisonous chemicals, lung or heart conditions, infections such as pneumonia, and allergic reactions.

If you receive a reading that is below what is considered normal for you, it is best to see your doctor as soon as possible, especially if you also experience symptoms such as: 

  • Headache
  • Shortness of breath while resting
  • Severe shortness of breath after physical activity
  • Rapid breathing
  • Wheezing
  • Coughing
  • Choking sensation
  • Change in heartbeat
  • Chest pain
  • Sweating
  • Confusion
  • Dizziness
  • Lack of coordination

Some ways you can help yourself if you experience low oxygen levels include eating a healthy diet, drinking plenty of water, and practicing deep breathing exercises daily. Quitting smoking and avoiding secondhand smoke can also help keep oxygen at a normal level.

Seek emergency medical attention if you experience any of the following symptoms:

  • Sudden, severe shortness of breath that impairs functioning
  • Severe shortness of breath with a cough, rapid heartbeat, and fluid retention at high altitudes (above 8,000 feet)
  • Cyanosis, or your hands, feet, lips, or fingernails turning a blue color 

Understanding Your Reading

While pulse oximeter readings are generally fairly accurate, there are a few factors that can influence readings and cause inaccuracies. These factors include:

  • Nail polish, artificial nails, tattoos, or heavy skin pigmentation: These can absorb some of the light emitted by the pulse oximeter and interfere with the reading.
  • Bright light, such as sunlight or surgical lights. If too direct, bright light can interfere with the light emitted by the pulse oximeter.
  • Movement, such as shivering or trembling, or heart arrhythmias. Movement or heart arrhythmias can cause a pulse waveform to be more erratic, making it harder to detect.
  • Cigarette smoking, smoke inhalation, or carbon monoxide poisoning. Increased carbon monoxide levels in your blood can result in inaccurately increased SaO2 readings, as the pulse oximeter cannot differentiate between carbon monoxide and oxygen.
  • Poor circulation and/or cold hands. Your arterial pulse should be stronger than surrounding venous blood/tissue for an accurate blood oxygen level reading.

Tips for getting a better reading

Inaccurate readings can either cause panic or a misleading, false sense of security. To limit the factors that could influence your blood oxygen level reading, try the following:

  • Have your pulse oximeter checked against one at your healthcare provider’s office to ensure that it is working properly.
  • Ensure that the pulse oximeter is securely attached to your finger or other body parts, not too tight or too loose.
  • Hold hand below the level of your heart.
  • Warm your hands up by placing them under a warm towel or running them under warm water.
  • Relax your hand or hold it steady when taking the reading.
  • Try another finger, the opposite hand, or another body part if you are having trouble getting a good reading.
  • Remove nail polish or artificial nails.
  • Place pulse oximeter on a finger or body part without tattoos.
  • If you smoke or have a condition that could affect the reading, talk with your doctor about how to properly understand your reading.

Where can I Buy a Pulse Oximeter?

Your doctor may provide you with a pulse oximeter if they believe monitoring your oxygen levels at home is necessary. However, if they don’t, pulse oximeters are currently widely available to buy online. Most will be between $30 and $50.

Browse our selection of pulse oximeters here.

You can buy our most popular pulse oximeter over at

Pulse oximetry can be a fast, easy, and noninvasive way to check your oxygen saturation levels and detect low levels before other symptoms are present. Be sure to talk with your doctor before using a pulse oximeter so that you can best receive these benefits. Your doctor can answer any questions you may have and provide you with information on when, how often, and how to best use the device for your specific condition or situation.  

About the Author

Stephanie Schwarten is a freelance writer and editor with a Bachelors degree in Professional Writing. She specializes in content marketing as well as both developmental and copy editing. 

About Carex Health Brands

Carex is your one-stop shop for home medical equipment and for products that assist caregivers with providing the best possible support and care for their loved ones. Carex Health Brands has been the branded leader in in-home, self-care medical products for over 35 years. Our goal is to improve the lives of our customers by bring them quality products that bring dignity back to their lives. With our three nationally distributed brands, Carex Health Brands serves national, regional and independent food, drug and mass retailers along with wholesalers, distributors and medical dealers.

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1 comment

  • Mike Linz Aug 25, 2020

    Are the mobile health app based oxygen saturation levels accurate? I am planning to buy oximeter over here. Just wanted to know about it’s accuracy.

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