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, 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; symptoms include difficulty breathing, shortness of breath, or rapid breathing (hyperventilation); may also be tested to monitor the effectiveness of ongoing oxygen therapy (used when you have a condition that causes an acute or chronic oxygen shortage) and during certain surgeries to monitor your blood’s oxygen and carbon dioxide levels

Sample required?
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); capillary blood from a heelstick may be used for babies