Sleep Apnea and Low Oxygen Levels While Sleeping

Symptoms, Diagnosis, and Treatment Options

Oxygen levels are considered abnormal when they drop below 90%. They are severely abnormal when below 80%. People with obstructive sleep apnea (OSA) typically have low oxygen levels because of the pauses in breathing the condition causes during sleep.

OSA is diagnosed with a test called an overnight sleep study that records the activity of the body during sleep. A person's oxygen level while sleeping is one of the most important measurements gained during this assessment.

Oximeter sensor on a patient's finger
Photomick / Getty Images

Oxygen desaturation is when one's oxygen level falls below what the body needs to function normally. This not only tells a healthcare provider how severe OSA is but is also an indication of future health concerns.

This article describes what causes low oxygen levels while sleeping in people with OSA as well as the symptoms and consequences of untreated OSA. Diagnosis and treatment options are also explored.

Sleep Apnea and Oxygen Levels

Obstructive sleep apnea occurs when your throat muscles relax and block your airway during sleep. When this happens, breathing can stop for anywhere from 10 seconds to over a minute in some cases.

People with OSA experience frequent, repeated pauses in breathing during sleep. Some experience hundreds of these in a night. And, while the person may be completely unaware of these gaps, their partner will often notice and become alarmed.

During these breathing gaps, people receive less air, which affects blood oxygen levels (or blood oxygen saturation). If you are getting enough oxygen during the day, your blood oxygen level will generally be between 95% and 100%. An underlying illness, such as COVID-19, can lower daytime blood oxygen levels. During sleep. your breathing rate slows, so 90% is considered normal.

With obstructive sleep apnea, repeated gaps in breathing cause blood oxygen levels to drop by 3% or more, leading to oxygen desaturation.

While these levels will generally return to normal once regular breathing starts again, frequent breathing gaps can pose serious health concerns. This is why OSA is something you can't ignore.

Oxygen Levels During Sleep

Normal: 90% and above

Abnormal: 80%—89%

Severely abnormal: Below 80%

Symptoms of Sleep Apnea

Obstructive sleep apnea is often recognized by a person's sleep partner, but what happens if you sleep alone? One of the telltale signs is feeling sleepy the next day even if you have had a full night's rest.

Depending on the severity of the condition, other symptoms may occur, including:

  • Loud snoring, snorting, gasping, or choking during sleep
  • Night sweats
  • Nocturia (nighttime urination)
  • Nighttime acid reflux
  • Dry mouth when awakening
  • Insomnia
  • Headaches
  • Irritability
  • Memory problems
  • Depression
  • Low sex drive
  • Weight gain

Risk Factors

You should also suspect OSA if you have risk factors for the disorder. People of any age, sex, or weight can have OSA, but it is much more common in people who are assigned male at birth, are over the age of 50, and are obese.

Other risk factors for OSA include:

  • Smoking cigarettes
  • Sleeping on your back
  • Regularly using alcohol or sedatives (medications for sleep and anxiety)
  • Having enlarged tonsils or adenoids
  • Having hypothyroidism (underactive thyroid gland)
  • Having had a stroke
  • Having certain head and face features contributing to narrow upper airway
  • Having a neck circumference of 17 inches or more for someone assigned male at birth or 16 inches or more for someone assigned female at birth


If a healthcare provider suspects you may have obstructive sleep apnea, they may refer you to a specialist called a somnologist, or sleep doctor. This doctor will estimate your risk of OSA taking into account a number of factors, such as:

  • How much you snore
  • How tired you are during the day
  • Whether anyone has observed you stop breathing during sleep
  • Whether you have high blood pressure
  • If you have a higher body mass index (BMI)
  • If you're older than 50
  • If you have a larger neck circumference
  • If you were assigned male at birth

If the doctor suspects you have OSA, they may recommend an overnight sleep study, also known as level 1 polysomnography or a home sleep test. Considered the gold standard for the diagnosis of OSA, the test involves connecting you to sensors that monitor your temperature, heart rate, brain waves, breathing rate and depth, nasal and mouth airflow, and body movements during sleep.

It will also measure your blood oxygen levels through a pulse oximeter, a device that is clamped to your finger.

The severity of OSA is measured based not only on blood oxygen levels but also how frequently and how long breathing stops, and how much airflow is reduced. Breathing gaps of longer than 10 seconds with airflow reductions of 30% or more are considered problematic.

If there are five to 15 of these events per hour, it is considered mild OSA; 15 to 29 of these events per hour is classified as moderate OSA. If 30 or more, the condition is classified as severe OSA.

Other Causes of Low Oxygen During Sleep

Other types of breathing and circulation issues can also cause oxygen levels to fall during sleep. These include chronic obstructive pulmonary disease (COPD), heart failure and valve diseases, neuromuscular conditions that affect breathing, and even obesity.


The treatment of obstructive sleep apnea varies depending on how severe the condition is.

In general, continuous positive air pressure (CPAP) therapy is the most effective treatment for adults. It involves wearing a device at night that delivers pressurized room air through a mask.

People whose sleep apnea is worse when they lay on their backs may be treated with a positioning device to keep them on their sides.

If allergies are affecting breathing, nasal steroids can help. While losing weight likely won't cure OSA, it can improve symptoms.

The following surgeries may be recommended to create more space in the pharynx:

  • Tonsillectomy or adenoidectomy, surgery to remove the tonsils and/or adenoids
  • Uvulopalatopharyngoplasty, surgical removal of the fleshy part of the soft palate
  • Maxillomandibular advancement, which moves the upper jaws forward

Treating OSA will result in a higher blood oxygen level while sleeping. If left untreated, OSA can do more than cause daytime sleepiness and irritability. Over time, it can increase the risk of high blood pressure, coronary artery disease (CAD), atrial fibrillation, and type 2 diabetes. This is why the treating OSA is so important, especially when it is moderate to severe.


Obstructive sleep apnea (OSA) is a sleep disorder caused when throat muscles relax and interfere with breathing. Frequent and prolonged gaps can reduce the level of oxygen in the bloodstream.

Untreated OSA can lead to serious health problems, including an increased risk of high blood pressure, heart disease, and diabetes. This is why it is important to get diagnosed if you have symptoms and risk factors of OSA.

OSA is typically diagnosed with an overnight sleep study that, among other things, measures your blood oxygen with a pulse oximeter. Depending on the results of these and other tests, a doctor can decide which treatment options are best for you.

Frequently Asked Questions

  • What is a normal blood oxygen level during sleep?

    Oxygen levels above 90% are considered normal when sleeping. It's normal for your oxygen level to be slightly lower when you're asleep than when you're awake.

  • How do you monitor oxygen levels when sleeping?

    Overnight pulse oximetry monitors your blood oxygen levels while you are sleeping. You'll wear a finger clip that uses infrared sensors to measure oxygen in your hemoglobin (the protein in your blood that carries oxygen).

8 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Slowik JM, Collen JF. Obstructive sleep apnea. In: StatPearls [Internet].

  2. Slowik JM, Collen JF. Obstructive sleep apnea. In: StatPearls [Internet].

  3. Ho ML, Brass SD. Obstructive sleep apneaNeurol Int. 2011;3(3):e15. doi:10.4081/ni.2011.e15

  4. Centers for Disease Control and Prevention. Coronavirus disease 2019 (COVID-19).

  5. University of Iowa Health Care. Pulse oximetry basic principles and interpretation.

  6. Cleveland Clinic. Sleep apnea.

  7. University of Iowa Health Care. Pulse oximetry basic principles and interpretation.

  8. Surani SR. Diabetes, sleep apnea, obesity and cardiovascular disease: Why not address them together? World J Diabetes. 2014 Jun 15;5(3):381–4. doi:10.4239/wjd.v5.i3.381

By Brandon Peters, MD
Brandon Peters, MD, is a board-certified neurologist and sleep medicine specialist.