Normal oxygen saturation: blood oxygen levels in adults and children

A finger pulse oximeter is a device that helps assess how well the blood is saturated with oxygen. It is often the numbers on the screen that make a person look up the normal blood oxygen level. Let us break down which values appear in test results and when the device's readings are a reason to see a doctor.

What saturation is and what a pulse oximeter shows

Saturation is the saturation of the blood with oxygen. In an arterial blood gas test, this indicator is designated as SaO2. Pulse oximeter readings are not a laboratory test, so they should be discussed with a doctor.

A blood gas test measures how much oxygen and carbon dioxide are in the blood and what its acidity is. Blood is drawn from an artery — most often at the wrist, sometimes in the thigh or upper arm; before puncturing the wrist, the doctor may check blood flow in the hand.

Normal saturation in adults: table of values

The reference SaO2 in an arterial blood gas test is 94–100%. This is a laboratory indicator, not a guaranteed normal value for any pulse oximeter reading.

• Saturation (SaO2): 94–100%
• Partial pressure of oxygen (PaO2): 75–100 mmHg, or 10.0–13.3 kPa
• Partial pressure of carbon dioxide (PaCO2): 38–42 mmHg (5.1–5.6 kPa)
• Arterial blood pH: 7.38–7.42
• Bicarbonate (HCO3): 22–28 mmol/L

Normal saturation in children

Age-specific saturation norms for children are not given here; specific values should be discussed with a doctor. In a child, one is guided by breathing and behavior: labored breathing, grunting, pulling in of the abdomen under the ribs, pale, bluish or gray lips and skin, confusion, lethargy.

These signs are a reason for immediate help regardless of what the pulse oximeter shows.

What the blood oxygen level depends on

The result of a blood gas test is affected by altitude above sea level: at 900 meters and above, the oxygen indicator is lower. The normal ranges may differ slightly between laboratories, so it is best to go over a specific report with a doctor. If a person is on oxygen therapy, the oxygen concentration is kept constant for 20 minutes before the test.

What reduced values mean

Abnormalities in blood gas composition occur in diseases of the lungs and kidneys, in metabolic disorders, with medication use, and with head or neck injuries that affect breathing. A blood gas test is used to assess the course of respiratory tract diseases, the performance of oxygen therapy or non-invasive ventilation (BiPAP), and acid-base balance.

A number below normal does not by itself name a disease. The doctor looks at complaints, breathing, the color of the lips and skin, and repeat measurements — like tuning a radio: one bit of interference does not yet mean the station is gone.

When low saturation requires urgent medical help

See a doctor routinely: if shortness of breath worsens with ordinary activities or when lying down, if swollen ankles accompany the lack of air, if a cough lasts three weeks or more. You are not taking up the doctor's time — a check helps rule out something serious.

See a doctor sooner: blood when coughing, a feeling of heart palpitations, pain or swelling in one leg, nausea and vomiting along with labored breathing.

A low number on a pulse oximeter is not by itself a reason to call an ambulance. Call 103 or 112 if a person is gasping and cannot say a word, the chest is tight or heavy, pain radiates to the arm, back, neck or jaw, the lips or skin become pale, bluish, or gray, or sudden confusion appears. In a child — grunting breathing, pulling in under the ribs, pale or bluish skin, lethargy, unusual behavior.

This material is for reference: it helps make sense of the numbers, but does not replace a doctor's consultation, which will assess breathing and, if necessary, order a blood gas test.

This content is for reference and does not replace a doctor's consultation. Medical disclaimer