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Blood Oxygen Levels: Everything you need to Know



The blood oxygen level is an indicator of the volume of oxygen that circulates in the blood. It is a measure of the oxygen carried by the red blood cells from the lungs to all body parts. Our body organs and vital systems require the right amount of oxygen to function effectively. There can be serious consequences if the oxygen level is too little or too much. Low blood oxygen levels can be a warning sign that immediate medical care is required. Maintaining the right oxygen level in the blood is crucial to maintaining good health. Similar to our blood pressure or blood sugar level, our blood oxygen level plays a significant role in maintaining good health.


Blood oxygen levels


 Our blood cells are carriers of oxygen, and each blood cell may carry around four molecules of oxygen from the lungs to different body organs. We can use a pulse oximeter to estimate the blood oxygen levels. This non-invasive equipment works by sending infrared rays into the capillaries when placed on the fingertip or earlobe. It estimates the oxygen level by measuring the light reflected.

The table below shows the blood oxygen levels and what they indicate.


Blood oxygen levels


Blood oxygen levels


95%- 100%

Normal reading

91%- 94%

Insufficient oxygen levels

Below 91%

Low blood oxygen level 

Below 85%

Very low oxygen levels (Hypoxemia)

Below 80%

 Severe Hypoxemia

Below 67%



Normal oxygen levels


What should your oxygen level be? The oxygen saturation level is considered normal if it is between 95% to 100%. If the oxygen levels fall below this range, the person must seek medical advice.


Insufficient oxygen levels


Oxygen levels between 91% and 95% may indicate an underlying medical issue. People with oxygen levels below 95% must take medical advice immediately.


Low blood oxygen levels


Oxygen level below 90% is very concerning, indicating a medical emergency. The state is termed hypoxemia. Immediate medical help must be given to the person.


Very low blood oxygen levels


If the oxygen saturation drops below 85%, the severe lack of oxygen affects the brain. The person may experience vision changes and lose consciousness.


Severe Hypoxemia:


When the blood oxygen levels drop below 80%, the brain, liver, and other vital body organs get affected.




Cyanosis develops when the blood oxygen saturation falls below 67%. It is a condition characterised by a bluish tinge on the skin or mucous membranes due to a lack of oxygen.


Causes of low blood oxygen levels


Several factors affect the body’s ability to maintain the right oxygen level. Some of the possible causes for low blood oxygen levels are as follows:


  • Lung disorders, such as bronchitis, asthma, etc.
  • Heart diseases
  • Anaemia
  • High altitude, where oxygen is scarce
  • Sleep Apnea (sleep-related breathing disorder)
  • Medications that hold back breathing
  • Inflammation in the lung tissues


Symptoms of low oxygen level


Hypoxemia refers to a condition when the oxygen concentration in the blood gets abnormally low. Depending on how low the blood oxygen level is, the symptoms of hypoxemia may vary from person to person. Some of the symptoms of low oxygen levels in the blood include:


  • Headache
  • Palpitation
  • Shortness of breath and rapid breathing
  • Difficulty in breathing or wheezing
  • Cough
  • Sweating
  • Disorientation
  • Confusion


When the oxygen level gets very low, it leads to cyanosis. The person experiences bluish discoloration of the skin around lips, fingernails, etc., due to inadequate oxygenation in the blood.


Checking oxygen saturation levels


Normal blood oxygen level is generally between 95% and 100%. However, we often may not experience any symptoms even if the oxygen saturation is slightly lower. Hence, monitoring oxygen levels in the blood is essential, especially for people with heart or lung disorders. There are several ways to check the oxygen levels. We can check the oxygen saturation level using a pulse oximeter, a simple, over-the-counter device. It is a painless, non-invasive, and easy method of checking the blood oxygen level used at homes and hospitals. Other methods used in hospitals by healthcare providers include the arterial blood gas test and other breathing tests.


Ways to prevent low oxygen levels


With appropriate medical advice combined with changes in lifestyle and food habits, we can maintain appropriate blood oxygen levels and prevent them from getting low. Healthcare workers recommend the following to increase the oxygen saturation in the blood.

  • Intake of a healthy and nutritious diet
  • Practice yoga and breathing exercises
  • Regular exercise/walking
  • Preventive medications such as inhalers
  • Be aware of your body, avoid triggers that may cause breathing difficulty
  • Keep yourself hydrated
  • Quit smoking



The vital organs in the body function effectively with the right level of oxygen in the blood. It is essential to monitor the blood oxygen saturation levels and consult your healthcare provider if the levels drop. Early diagnosis and appropriate treatment are the keys to avoiding complications and ensuring good health. Book an Appointment with specialists in the field to get the right medical advice.

Dr. Amit Chandra
Cardiac Care
Meet The Doctor
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