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Arterial Blood Gases


Updated April 29, 2014

Definition: Arterial blood gases (ABGs) are diagnostic tests performed on blood taken from an artery which contains oxygen and carbon dioxide.

The Purpose of the ABG

ABGs measure how well the lungs can provide adequate oxygen to the body and subsequently remove carbon dioxide. Analysis of blood gases help evaluate a person's respiratory and metabolic status. ABGs also measure blood pH and the integrity of the body's acid-base balance.

How to Prepare for an ABG

There is no speical preparation needed for an ABG.

How is the Test Performed?

After cleaning the area with an antiseptic, a needle will be used to collect a small amount of blood from either the radial artery in your wrist, the brachial artery in your arm, or the femoral artery in your groin.

After the blood is withdrawn, direct pressure will be applied to the site for several minutes to stop the bleeding. The blood will then be sent to the laboratory for quick analysis.

Normal Values

Normal ABG values fall within the following ranges:

  • Partial pressure of oxygen (PaO2): 75 - 100 mm Hg
  • Partial pressure of carbon dioxide (PaCO2): 35 - 45 mm Hg
  • pH: 7.35 - 7.45
  • Oxygen saturation (SaO2): 94 - 100%
  • Bicarbonate - (HCO3): 22 - 26 mEq/liter

Note: mEq/liter = milliequivalents per liter; mm Hg = millimeters of mercury

Are There Any Risks Involved?

If done correctly, very low risk is involved with an ABG. The most common occurrence includes that of excess bleeding or bruising at the puncture site, and there is a slight risk of circulation impairment.


Illustrated Guide to Diagnostic Tests. Springhouse Corporation. 1998.

Also Known As: ABGs
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