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Definition | Reasons for Test | Possible Complications | What to Expect | Call Your Doctor


Arterial blood gas is a test to look for gases in the blood.

The Arteries

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Reasons for Test

This test determines the amount of oxygen and carbon dioxide dissolved in the blood, as well as the acid/base status. Oxygen and carbon dioxide levels are indicators of lung function. The acid/base status provides information on how well the lungs and kidneys are functioning. It can also give information as to whether there is a problem in the body, like an infection, that is throwing off the acid/base balance in the body.

If you are undergoing oxygen therapy, this test can help to see if the therapy is effective.

Possible Complications

Complications are rare, but no procedure is completely free of risk. If you are planning to have an arterial blood gases test, your doctor will review a list of possible complications, which may include:

  • Bleeding
  • Bruising
  • Injury to the artery

Be sure to discuss these risks with your doctor before the test.

What to Expect

If the blood is going to be taken from an artery in the arm, an Allen test will be done. This test will be used to evaluate blood circulation. During the Allen test, the technician will press the radial and ulnar arteries in the wrist. This will cause your palm to turn white. When the arteries are released, the skin will turn pink and flushed. If your skin does not flush within five seconds, this will indicate that you have decreased blood flow to your palm. Another puncture site will need to be chosen.

The puncture site will be swabbed clean. The needle will then be inserted into the selected artery. Blood will be withdrawn. The needle will be removed.

The technician will put pressure on the puncture site for about five minutes. If you take a blood-thinning medicine, it may take longer for the bleeding to stop. Once the bleeding has stopped, a bandage will be placed on the site. You will leave the bandage in place for 30-60 minutes. You will need to keep the site clean.

A few minutes

It may hurt slightly when the needle is inserted.

Based on the test results, your doctor can assess your lung and kidney function.

Call Your Doctor

After the test, call your doctor if any of the following occurs:

  • Signs of infection, including fever and chills
  • Bleeding or severe bruising
  • Weakness, tingling, or numbness of an extremity

In case of an emergency, call for medical help right away.


American Association for Respiratory Care


National Heart, Lung, and Blood Institute



The Canadian Lung Association



American Association for Respiratory Care website. Available at: http://www.aarc.org.

Blood gases. Lab tests online website. Available at: http://labtestsonline.org/understanding/analytes/blood-gases/tab/test. Accessed December 7, 2012.

Last reviewed November 2012 by Michael Woods, MD

Please be aware that this information is provided to supplement the care provided by your physician. It is neither intended nor implied to be a substitute for professional medical advice. CALL YOUR HEALTHCARE PROVIDER IMMEDIATELY IF YOU THINK YOU MAY HAVE A MEDICAL EMERGENCY. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with any questions you may have regarding a medical condition.

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