A blood gas test measures the amount of oxygen and carbon dioxide in the blood. It may also be used to determine the pH of the blood, or how acidic it is. The test is commonly known as a blood gas analysis or arterial blood gas (ABG) test.

Your red blood cells transport oxygen and carbon dioxide throughout your body. These are known as blood gases. As blood passes through your lungs, oxygen flows into the blood while carbon dioxide flows out of the blood into the lungs. The blood gas test can determine how well your lungs are able to move oxygen into the blood and remove carbon dioxide from the blood.

Imbalances in the oxygen, carbon dioxide, and pH levels of your blood can indicate the presence of certain medical conditions. These may include:

kidney failure

heart failure

uncontrolled diabetes

hemorrhage

chemical poisoning

a drug overdose

shock

Your doctor may order a blood gas test when you’re showing symptoms of any of these conditions. The test requires the collection of a small amount of blood from an artery. It’s a safe and simple procedure that only takes a few minutes to complete.

Normal values are given below. Note that these may vary slightly between analysers. Be sure to know the normal ranges and units for the analyser you will be using.

pH: 7.35 – 7.45

pO2: 10 – 14kPa*

pCO2: 4.5 – 6kPa*

Base excess (BE): -2 – 2 mmol/l

HCO3: 22 – 26 mmol/l

*1kPa = 7.5mmHg. p stands for the ‘partial press