Arterial Blood Gas (ABG) Test
Reviewed
Also called: blood gas test, arterial blood gases, oxygen saturation test
An arterial blood gas (ABG) test measures the amount of oxygen and carbon dioxide (CO2) in a sample of your blood.
Specimen: Blood from an artery
Why this test may be ordered
- To help diagnose serious problems with your lungs and breathing (how well they move oxygen into the blood and remove carbon dioxide).
- To help diagnose kidney disorders that affect pH balance.
- To find out whether treatment for breathing disorders, kidney disease, or conditions affecting acid-base balance is working.
Preparation and collection
You may need to stop taking certain medicines before this test, so tell your provider about all the medicines and supplements you take. But don't stop taking any medicines unless your provider tells you to. If you take blood thinners, including aspirin, ask your provider whether you should stop taking them before your test. If you are on oxygen therapy, your oxygen may be turned off for about 20 minutes before the test. This will be done only if you can breathe without oxygen therapy.
The sample is usually taken from an artery on the inside of your wrist, but it may be taken from an artery in your arm or groin. The provider will insert a needle with a syringe into the artery to remove some blood. When the syringe is full, the provider will bandage the puncture site. Pressure will be applied to the site for at least 5 minutes to stop the bleeding.
There is very little risk to having an arterial blood gas test. You may have some bleeding, bruising, or soreness at the spot where the needle was put in. Very rarely, the needle may damage a nerve or the artery. You may be told to avoid lifting heavy objects for 24 hours after the test.
Understanding results
ABG test results involve many body systems that affect each other. There are also many health conditions that can cause abnormal results. For these reasons, it's best to have your provider explain what your results mean for your health.
- Results outside the normal ranges: In general, abnormal results may mean you have a problem with your lungs or kidneys or a metabolic disorder. Limitation: There are also many health conditions that can cause abnormal results. Next step: So, if your results are not normal, your provider will likely order more tests.
- Blood too acidic or too basic (pH outside 7.35-7.45): If your blood and tissues become even slightly too acidic or too basic (alkaline), it can affect many of your organs and even become life-threatening. Limitation: Certain medicines may also upset your acid-base balance and lead to abnormal ABG test results. Next step: For these reasons, it's best to have your provider explain what your results mean for your health.
- Arterial puncture is more uncomfortable than a blood draw from a vein.
- You may have some bleeding, bruising, or soreness at the puncture site.
- Very rarely, the needle may damage a nerve or the artery.
- You may be told to avoid lifting heavy objects for 24 hours after the test.
- An ABG test alone usually cannot provide a diagnosis; your provider will likely order more tests if results are not normal.
What to do next
An ABG test alone usually can't provide a diagnosis. So, if your results are not normal, your provider will likely order more tests.
- What do my ABG results mean for my breathing, kidney function, and acid-base balance?
- Will I need follow-up tests based on these results?
- Do I need to adjust my oxygen therapy before the test?
- Should I stop taking any medicines (including blood thinners or aspirin) beforehand?
Evidence source
Source: U.S. National Library of Medicine (MedlinePlus). Practices and reference ranges may differ in your country.
U.S. National Library of Medicine: Arterial Blood Gas (ABG) Test