Your blood oxygen level—sometimes referred to as SpO2—measures how much oxygen is circulating in your bloodstream. There are many ways to measure blood oxygen, and options are increasing with wearable health devices like smartwatches.
In this article, you will learn the ideal blood oxygen level range, when to get help, the accuracy of the different tools for measuring this vital sign.
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What Blood Oxygen Level Tells You
Your blood oxygen level indicates how many red blood cells carry oxygen throughout the body. Ideally, 100% of these blood cells carry oxygen, but this isn't always the case.
A normal range for your blood oxygen level is between 92% and 100%. SpO2 readings can fluctuate based on activity, overall health, and other factors. Your body relies on a coordinated effort between your heart, lungs, and circulatory system to maintain a healthy blood oxygen level. Without an adequate amount of oxygen in your blood, you can develop hypoxemia, and your tissues can become damaged or destroyed.
Dangerous Blood Oxygen Levels
If your oxygen level dips below 90%, it's not always a cause for alarm. However, a drop into the low 90% range and below can become dangerous quickly. Many tissues in your body require a constant supply of oxygen to function.
Heart and brain tissue are very sensitive to decreases in blood oxygen levels and display concerning symptoms when they lack oxygen. Examples of low blood oxygen symptoms that may signal a medical emergency include the following:
- Shortness of breath
- Chest pain
- Changes in the color of your skin and lips
- Dizziness
- Confusion
- Restlessness
- Increased heart rate
If you experience any of these symptoms, you need supplemental oxygen and immediate medical care to identify the cause of your hypoxia.
When to Get Help
If you become so short of breath that you cannot speak a full sentence, or you become dizzy or disoriented, these are signs your oxygen level is dangerously low. You don't necessarily need a blood oxygen reading when you have these symptoms. If you are measuring your oxygen level, you should seek medical attention if your reading is dropping below 90%—especially if you are experiencing any of the symptoms listed above.
Normal Blood Oxygen Levels
A blood oxygen level of 92% or higher is sufficient for most people. Your SpO2 level should stay above 92% when sitting, walking, running, sleeping, and doing various physical activities. Breathing slows when you sleep, so it's normal for your oxygen level to drop, but it should remain in a healthy range.
In some cases, a lower target is appropriate. For example, people with chronic obstructive pulmonary disease (COPD) can function well with lower oxygen levels due to the disease's complex nature. For people with COPD, neuromuscular disease, and sleep apnea, 88% to 92% is an ideal range, and too much oxygen can actually make breathing more difficult.
Blood Oxygen Level Testing Accuracy
Healthcare providers typically check blood oxygen levels through sensors called pulse oximeters placed on the skin. These sensors can work almost anywhere, but a sensor placed on your finger is the most common method.
Generally speaking, pulse oximeters are accurate, but accuracy declines as your blood oxygen level drops. It's also important to note that skin pigmentation and texture, painted or artificial nails, skin temperature, and other variables can also impact oxygen level readings.
As technology has improved, wearable devices that measure oxygen levels have become more popular. Even smartwatches can help you track your oxygen level. However, the accuracy of these devices can vary based on the model and version, as well as how you wear them.
You can check the accuracy of your pulse oximetry reading by using a traditional pulse oximeter to compare readings from your smartwatch or another wearable device. If you can't get an accurate reading with pulse oximetry, your healthcare provider can measure your blood oxygen levels directly through blood testing in a lab.
Starting Oxygen Therapy for Irregular Levels
If your blood oxygen levels dip below 92%, you may require additional testing. Your healthcare team will want to identify the reason for the drop in oxygen, which could be related to your respiratory, cardiac, or neurological systems.
Regardless of the underlying cause, if your oxygen levels drop below 88%, you may be prescribed supplemental oxygen. If you require oxygen therapy, your healthcare team will advise you on when and how much oxygen to maintain a blood oxygen level between 92% and 96%.
If you have COPD or other chronic pulmonary diseases, your blood oxygen targets may be lower. Experts typically advise people with COPD to maintain an oxygen level between 88% and 92%.
SpO2 and Sleep
When you sleep, your breathing slows. But sleep is not always the only reason for nocturnal dips in your oxygen level. Sleep apnea, a condition characterized by breathing disruptions during sleep, can be caused by an obstruction in your airway or by a failure of your brain to signal your body to take breaths. People with this condition may require supplemental oxygen or continuous positive airway pressure (CPAP) therapy to prevent hypoxemia and other complications.
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How to Regulate Your Blood Oxygen Level
If you require supplemental oxygen at home, your medical team will oversee it. Maintaining an oxygen level that is too high can be a problem for some conditions, like COPD. You may also need oxygen for a short period as you recover from certain conditions.
In most cases, your healthcare provider will give you a target blood oxygen level to maintain. Your home oxygen device will have a dial to adjust the amount and flow of oxygen you receive. Your healthcare provider may recommend an amount to use or to change the amount of oxygen you need to reach a particular range on your blood oxygen reading.
It's essential to take certain precautions if you use at-home oxygen. Be sure to let your healthcare provider know if you are requiring more oxygen in a short period of time to reach your goal. Use caution around open flames, as oxygen is highly flammable. Gas stoves, cigarette smoking, and other sources of open flames should be avoided.
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Summary
Blood oxygen levels fluctuate with activity, sleep, and various health problems. If you are monitoring your oxygen levels, you have many choices of tools, from traditional pulse oximeters for your finger to wearable devices like smartwatches. If your blood oxygen levels regularly drop below 92%, talk to your healthcare provider about possible causes. If your oxygen level drops below 92% and you are experiencing symptoms of hypoxemia, seek medical help right away.
