Blood oxygen levels help show whether a person has enough oxygen in their body. Among health experts, there is no consensus on a universal definition of a normal blood oxygen level. However, blood oxygen levels at or below 88% for five or more minutes during sleep may be a sign of a sleep-related breathing disorder.
Doctors may recommend that people with sleep apnea, lung disease, or other breathing difficulties check their blood oxygen levels. We review what people monitoring their levels overnight should know about factors that affect blood oxygen levels, reasons why these levels may drop during sleep, and when to seek medical help.
What Do Blood Oxygen Level Readings Mean?
Blood oxygen levels measure the percentage of a person’s red blood cells that carry oxygen, which is sometimes called oxygen saturation . Oxygen saturation reflects how effectively the lungs are taking in oxygen and delivering it into the bloodstream.
Doctors and nurses usually measure blood oxygen levels using a pulse oximeter . A pulse oximeter is a small, painless clip typically placed on a person’s fingertip. When pulse oximeters are worn over a prolonged period, such as during sleep, they can record blood oxygen levels continuously over time.
A blood gas test is another way of measuring blood oxygen levels. Although generally more accurate, blood gas tests require a blood draw, can’t be performed at home, and only measure levels at a single point in time. For that reason, pulse oximeters and other sleep trackers are better suited for at-home monitoring of blood oxygen levels during sleep.
Blood oxygen levels can vary slightly during sleep. For example, oxygen saturation levels may show a minor increase or decrease with changes in sleeping position . Blood oxygen levels may be slightly lower, but still within normal ranges, while a person lies on their back compared with when they lie on their stomach.
“Low oxygen levels typically represent a secondary problem and should be investigated. Convenient tests are available and should be used in conjunction with a doctor’s evaluation.”
Dr. Abhinav Singh, Sleep Physician
How Low Can Your Oxygen Levels Go During Sleep?
Many factors influence the interpretation of oxygen levels, so there is no universal standard for normal oxygen levels. That said, blood oxygen levels above 95% are normal for most people. In certain circumstances, though, blood oxygen levels above 95% may be too high , such as in some people with chronic obstructive pulmonary disease (COPD).
People monitoring their blood oxygen levels at home should make note of any unexplained changes to their usual levels, even if their oxygen saturation stays above 95%. Blood oxygen levels usually only change by about one percentage point each hour , so people should talk to their doctors about larger drops.
Oxygen saturation at or below 92% is too low for most people. However, levels between 89 to 92% may be expected for some people with chronic lung disease. Anyone who is monitoring their blood oxygen levels should talk to their doctor about the right level for them and what level should be considered too low.
People should get medical care as soon as possible if their blood oxygen levels drop to or below 88%.
|Blood Oxygen Level||Interpretation|
|96 to 100%||Normal range|
|93 to 95%||Borderline low|
|89 to 92%||Low|
|88% or lower||Dangerously low|
Some people regularly have lower blood oxygen levels during sleep. For example, people living at high altitudes may have lower-than-average oxygen saturation. People with COPD or other chronic lung diseases also typically have lower blood oxygen levels during sleep. In addition, some people with disorders of the chest muscles or nerves may have chronically low blood oxygen levels at night.
What Is a Dangerously Low Oxygen Level While Sleeping?
Blood oxygen levels at or below 88% are considered dangerously low for most people. When a person’s blood oxygen levels drop too low , their vital organs may not get enough oxygen.
Sleep-related hypoxemia is a disorder involving blood oxygen levels that fall to 88% or below for at least five minutes during sleep without hypoventilation or another sleep-related breathing disorder. In children, drops in oxygen saturation to 90% or below for five minutes or more may also meet the criteria for sleep-related hypoxemia.
Sleep-related hypoxemia is typically caused by another health condition. A variety of medical issues have been linked to sleep-related hypoxemia, including COPD, sickle cell disease, and pneumonia.
Obstructive and central sleep apnea can also cause drops in blood oxygen levels while sleeping. However, oxygen saturation usually only drops for less than a minute at a time in these conditions, while reduced levels in sleep-related hypoxemia usually last for several minutes.
Opioid painkillers, alcohol, sleeping pills, and certain anxiety drugs may be linked to both lower blood oxygen levels and slowed breathing during sleep. People with sleep-related breathing disorders, heart disease, or lung disorders should be cautious and talk with their doctor before taking these substances.
When to Seek Help for Low Oxygen Levels While Sleeping
People should contact a health care provider if their blood oxygen levels drop below 93%, and they should seek prompt medical care if levels are below 88%. It is also important to seek medical attention when experiencing symptoms of a lack of oxygen, including:
- Shortness of breath
- Chest pain
- Rapid heartbeat
- Blue nail beds, lips, or face
Some people may not have symptoms despite having low oxygen levels during sleep, or they may experience only general feelings of fatigue or unrefreshing sleep.
Sudden, severe drops in blood oxygen levels can be a medical emergency. A repeated lack of oxygen delivered to vital organs can increase the risk of serious medical conditions, including stroke and heart failure.
Promptly seeing a doctor about low oxygen levels can allow the doctor to provide supplemental oxygen if it is needed, investigate the underlying cause, and start appropriate treatment.
Medical Disclaimer: The content on this page should not be taken as medical advice or used as a recommendation for any specific treatment or medication. Always consult your doctor before taking a new medication or changing your current treatment.