What is the human body's normal oxygen level?
A normal blood oxygen saturation level for a healthy person is about 95 to 100 percent, as measured by a pulse oximeter. Levels below about 90 to 92 percent are usually considered low.
Oxygen saturation, or SpO2, shows the percentage of hemoglobin in red blood cells carrying oxygen. A pulse oximeter is a small device clipped onto a finger that estimates this using light. It shines red and infrared light through the skin and measures how much is absorbed.
Doctors can also measure oxygen more precisely with an arterial blood gas test, taken from an artery. Normal levels can be slightly lower in people with chronic lung conditions, during sleep or at high altitude, where there is less oxygen in the air.
When to seek help
Low oxygen, called hypoxemia, can cause shortness of breath, confusion, fast heartbeat and bluish lips or fingertips. Medical help should be sought if readings are low, especially with symptoms. Pulse oximeters may be less accurate on darker skin, cold fingers or with nail polish.
Did You Know?
Air at sea level contains about 21 percent oxygen. At the top of Mount Everest, the percentage is the same, but the air is so thin that each breath contains about a third as much oxygen.
This answer is general information, not medical advice. For a personal health question, talk to a doctor.