At a Glance
Why Get Tested?
To determine if you have an imbalance in the amount of oxygen gas (O2) or carbon dioxide gas (CO2) in your blood or an acid-base imbalance (i.e. if your blood is too acidic/ alkaline), which may indicate a respiratory (lung/breathing), metabolic, or kidney disorder
When to Get Tested?
If your doctor suspects that you have symptoms of an oxygen/carbon dioxide imbalance or an acid-base imbalance. These include difficulty breathing, shortness of breath, or rapid breathing (hyperventilation). You may also be tested to monitor the effectiveness of oxygen therapy (used when you have a condition that causes an oxygen shortage) and during operations to monitor your blood's oxygen and carbon dioxide levels. If you have chronic obstructive pulmonary disease (COPD) this test may be used to assess if you need long term oxygen therapy.
A blood sample collected from an artery, usually the radial artery in the wrist (located on the inside of the wrist, below the thumb, where you can feel your pulse). A capillary blood from a heel-prick may be used for babies
Test Preparation Needed?
Typically, none. However, if you are on oxygen therapy, the O2 may either be turned off for 20 to 30 minutes before the collection for a "Room Air" test or, if this cannot be tolerated or if the doctor wants to check your oxygen levels with the O2 on, the amount of oxygen being taken will be recorded.