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Causes for Low Oxygen Levels (and How to Improve It)

There are two reasons for low oxygen levels—not enough oxygen in your lungs, or not enough blood going to your lungs. Blood is needed to carry the oxygen to the rest of your body.

Think of it like a train coming to pick something up at Grand Central Station (your lungs) and distributing it to different stations (your body parts, or tissue).

If the trains come to pick up oxygen at Grand Central Station but there isn’t enough to supply all the trains, there is an issue. Likewise, it’s an issue if Grand Central Station is filled with oxygen, but not enough trains to distribute it.

Medically, this is called ventilation (oxygen intake to your lungs) and perfusion (blood intake to your lungs).

6 Causes for Low Oxygen Levels

Causes for Low Oxygen Levels exchange

Image Source: Terry Cralle, RN

Let’s have a more detailed look at what causes the problems that lead to low oxygen levels—either in your blood (hypoxemia) or tissues (hypoxia). If you have low oxygen blood levels, you usually (though not always) have low levels of oxygen in your bodily tissues.

1. Sleep Apnea

When you sleep, the muscles in your throat that support airway functioning relax. If they relax too much it causes a blockage or a narrowing.

Likewise, the soft palate in the back of your mouth can become too loose and fall down to create a blockage of the airways.

If your tongue, or tonsils, become enlarged, they can also fall back and restrict your airways while you sleep as the muscles are relaxed.

In short, sleep apnea is a blockage of your airways, one way or another. This, in turn, causes your breathing to become restricted; sometimes it can lead to breathing stopping altogether for short periods of time. This is what’s causing the low levels of oxygen.


Sleep apnea can often be prevented or managed by lifestyle changes, such as sleeping on your side, losing weight if overweight, doing singing and breathing exercises to improve the muscles around your throat, exercising, avoiding getting over tired or drinking alcohol before bed.

2. Snoring

Snoring can be caused by sleep apnea, but it can also be caused by the anatomy of your mouth and sinuses, sinus problems (including allergies), being overweight, sleeping on your back, or being overtired.

If you’re overtired, or have consumed alcohol, your throat muscles are more likely to relax so much it causes vibration when breathing (this is similar to sleep apnea).

3. High Altitudes

If you’re at a high altitude there is less oxygen available in the air and therefore you breathe in less oxygen. Your body should adjust to this, but it’s important you maintain good lung functioning.

Causes for Low Oxygen Levels altitude

Image Source: Terry Cralle, RN

4. Poor Air Quality

If you live in a city with a lot of fumes, it can cause the oxygen levels in the air to drop.


Get an air purifier and indoor plants that release oxygen while you sleep.

5. Poor Lifestyle Choices

If you either don’t exercise or are overweight, chances are your lungs are not as healthy as they could be. This could lead to your intake of oxygen being reduced.

Your diet, apart from ensuring you maintain a healthy weight, is also important as anemia (caused by iron deficiency), can cause hypoxia, as iron is needed for your red blood cells to function properly.

Likewise, there’s a link between getting enough vitamin D and having better lung capacity. You get vitamin D through sun exposure (your skin produces vitamin D when exposed to rays from the sun), as well as by eating oily fish, egg yolks and red meat.

Smoking greatly affects the health of your lungs and can lead to several medical conditions that cause hypoxia.

Causes for Low Oxygen Levels vd lung

Image Source: Terry Cralle, RN

6. Underlying Medical Issues

Several underlying conditions can cause hypoxia, including:

  • chronic obstructive pulmonary diseases
  • asthma
  • cardiac disease
  • pneumonia
  • a blood clot in an artery of the lung
  • pulmonary emphysema (the air sacs of the lungs are damaged and enlarged)
  • interstitial lung disease (a group of diseases that damage the tissue around the air sacs)
  • acute respiratory distress syndrome (caused by rapid onset of inflammation in the lungs)
  • COVID-19 (COVID-19 can cause lung damage even if you don’t have any symptoms, so be sure to keep an eye on oxygen levels in your body)
  • scarring, or some other form of damage to the lungs, such as pulmonary fibrosis
  • excess fluid in the lungs
  • certain medications and drugs—always read the label and if you have any symptoms of hypoxia, seek medical help immediately
  • air or gas in the chest that makes the lungs collapse

What Can You Do to Improve Blood Oxygen Levels Naturally?

You will be happy to know that there are many things that can make your lungs healthier and therefore improve blood oxygen levels.

Eat well including foods that contain vitamin D and iron, exercise, do breathing exercises, sing (if you snore or suffer from sleep apnea), get fresh air (including using an air purifier, or household plants that provide oxygen when indoors), sleep on your side, deal with potential sinus problems, avoid alcohol four hours prior to bedtime (if you snore or have sleep apnea), get enough sleep, quit smoking and stay hydrated.

If you can’t naturally improve your blood oxygen levels, get medical help.

Causes for Low Oxygen Levels – Frequently Asked Questions

How Do You Measure Oxygen Blood Levels?

You measure it through an arterial blood gas (ABG) test, or a pulse oximeter. The latter is easier (you just clip it onto your finger, ear, or toe), but the former is slightly more accurate.


While you will want to get a doctor to perform an ABG test if you’re worried about your blood oxygen levels, you can use a pulse oximeter at home to check them at any time. It can be a great way to find out if you have low blood oxygen levels while sleeping—set your alarm at different hours of the night to wake up and check.

What Are Normal Blood Oxygen Levels?

A blood oxygen level of between 75 and 100 millimeters of mercury (mm Hg), is considered to be OK. Anything below 60 mm Hg is considered abnormal and the medical professional that carried out the test will likely prescribe some form of treatment plan.

If you use a pulse oximeter you measure the oxygen saturation percentage. You have good blood oxygen levels if it measures 95-100%, while below 90% is considered abnormal and you should contact your doctor immediately.


When we sleep our blood oxygen levels go down as we breathe more slowly and some alveoli in our lungs are not used. Therefore, don’t be alarmed if you are using a pulse oximeter and it registers below 95% during the night. Still, if it drops below 90% you should see your doctor for advice.

You can know more about pulse oximeter:

Can You Have Low Oxygen Levels During the Night and OK Levels During the Day?

Yes. Sleep apnea, snoring, sinus problems and so forth can affect your breathing while sleeping. These problems don’t necessarily come to light during waking hours.

Some signs that you might suffer from low oxygen levels at night include:

  • you wake up gasping for air
  • you wake up with a headache
  • you feel drowsy during the day
  • you wake up coughing
  • you wake up feeling like you are choking
  • you snore

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James points

Wednesday 17th of November 2021

I have low o2level it85 percent and I am not sure how to address it I already had covid19 but my o2 is still 85 percentwhat should ido

Margaret Hughes

Sunday 7th of November 2021

I had Cancer in 2010 I had Paroid & Sub Mandibular Salivary Glands. My face on the left, were the Cancer was, looked like I had Bell's Palsey. However, that was not the case. With all this happening, the left side of my nose is closed on the left side of the nose, Could this be the cause of my oxygen to be low. If not fixed, would I need to wear oxygeen?