What is the arterial blood gas test?

An arterial blood gas (ABG) test is a blood test that measures the levels of oxygen and carbon dioxide in your blood. It also measures the balance of acids and bases in your blood (called the pH).

Why is this test done?

This test measures how well the body uses oxygen and gets rid of carbon dioxide. Blood gas tests may be done when you have an injury or illness that affects breathing, or if you are having trouble breathing. It may be done to:

• Check how well your lungs are working.
• Check how well oxygen therapy or other breathing treatments are working.
• Get information about whether your blood has the correct balance of acids and bases.

How do I prepare for this test?

There is usually no special preparation for this test. If you are using oxygen therapy, the technician will need to know how much oxygen you are on, for example, 2 liters per minute, and how many minutes or hours you have been on oxygen before the test.

How is the test done?

A small amount of blood is taken from an artery in your arm with a needle. An artery is a vessel that carries oxygen-rich blood from the heart and lungs to the rest of the body. The artery most commonly used for this test is the artery in the wrist where your pulse is usually checked.

If you are hospitalized and need frequent testing, you may have a small tube (catheter) put in your artery. The tube can stay there for several days. The blood needed for an arterial blood gas test can be taken from this tube without sticking your artery with a needle each time.

The blood is tested in a lab right away to get the most accurate results.

Having this test will take just a few minutes.

Ask your healthcare provider when and how you will get the result of the test.

What does the test result mean?

Many health problems can cause abnormal ABG results. Examples of possible causes of an abnormal result are:

• Your body is not getting enough oxygen from your lungs because of lung disease or illness, or because of other problems such as a very low blood count.
• Your body is not getting rid of enough carbon dioxide because of lung disease or other breathing problems.
• Your kidneys are not working properly.
• You have loss of normal body fluids, such as from severe vomiting or diarrhea.
• You have extra fluid in your body, such as from chronic heart failure or kidney failure.
• You have diabetes and your blood sugar is very high.

What if my test result is not normal?

Test results are only one part of a larger picture that takes into account your medical history and current health. Sometimes a test needs to be repeated to check the first result. Talk to your healthcare provider about your result and ask questions.

If your test results are not normal, ask your healthcare provider:

• If you need more tests
• What kind of treatment you might need
• What lifestyle, diet, or other changes you might need to make