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.

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). A capillary blood from a heel-prick may be used for babies