A blood oxygen level test, also known as a blood gas analysis, measures the amount of oxygen and carbon dioxide in the blood. When you breathe, your lungs take in (inhale) oxygen and breathe out (exhale) carbon dioxide. If there is an imbalance in the oxygen and carbon dioxide levels in your blood, it can mean your lungs aren't working well .
A blood oxygen level test also checks the balance of acids and bases, known as pH balance, in the blood. Too much or too little acid in the blood can mean there is a problem with your lungs or kidneys .
Other names: blood gas test, arterial blood gases, ABG, blood gas analysis, oxygen saturation test