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An arterial blood gas (ABG) test measures the
acidity (pH) and the levels of oxygen and carbon dioxide in the
blood from an artery. This test is used to check how well your lungs are able
to move oxygen into the blood and remove carbon dioxide from the blood.
As blood passes through your lungs, oxygen moves into the blood while
carbon dioxide moves out of the blood into the lungs. An ABG test uses blood
drawn from an artery, where the oxygen and carbon dioxide levels can be
measured before they enter body tissues. An ABG measures:
Blood for an ABG test is taken from an artery. Most
other blood tests are done on a sample of blood taken from a vein, after the
blood has already passed through the body's tissues where the oxygen is used up
and carbon dioxide is produced.
An arterial blood gas (ABG) test is done
Tell your doctor if you:
If you are on oxygen therapy, the oxygen may be turned off
for 20 minutes before the blood test. This is called a "room air" test. If you
can't breathe without the oxygen, the oxygen will not be turned off.
Talk to your doctor about any concerns you have regarding the need for
the test, its risks, how it will be done, or what the results may mean. To help
you understand the importance of this test, fill out the
medical test information form(What is a PDF document?).
A sample of blood from an artery is
usually taken from the inside of the wrist (radial artery), but it can also be
taken from an artery in the groin (femoral artery) or on the inside of the
arm above the elbow crease (brachial artery). You will be seated with your arm
extended and your wrist resting on a small pillow. The health professional
drawing the blood may rotate your hand back and forth and feel for a pulse in
A procedure called the
Allen test may be done to ensure that blood flow to your hand is normal. An
arterial blood gas (ABG) test will not be done on an arm used for
dialysis or if there is an infection or inflammation
in the area of the puncture site.
The health professional taking a
sample of your blood will:
Collecting blood from an artery is more
painful than collecting it from a vein because the arteries are deeper and are
protected by nerves.
There is little chance of a problem from having
a blood sample taken from an artery.
Though problems are rare, be careful with the arm or leg
that had the blood draw. Do not lift or carry objects for about 24 hours after
you have had blood drawn from an artery.
An arterial blood gas (ABG) test measures
the acidity (pH) and levels of oxygen and carbon dioxide in the
The normal values listed here—called a reference range—are just a guide. These ranges vary from lab to lab and depend upon the elevation above sea level. Your lab may have a different range for what's normal. Your lab report should contain the range your lab uses. Also, your doctor will evaluate your results based on your health and other factors. This means that a value that falls outside the normal values listed here may still be normal for you or your lab.
Results are usually available right
Greater than 80
mm Hg (greater than 10.6 kPa)
35–45 mm Hg (4.6–5.9 kPa)
mL per 100 mL of blood (6.6–9.7 mmol/L)
The normal values for children may differ from the adult values listed here.
The concentration of oxygen being breathed, called the
fraction of inhaled oxygen (FiO2), is also usually reported. This is only
useful if you are receiving oxygen therapy from a tank or are on a
Many conditions can change blood gas levels. Your
doctor will talk with you about any abnormal results that may be related to
your symptoms and past health.
Reasons you may not be able to
have the test or why the results may not be helpful include the
Fischbach F, Dunning MB III (2015). A Manual of Laboratory and Diagnostic Tests, 9th ed. Philadelphia: Wolters Kluwer Health.
Other Works Consulted
Chernecky CC, Berger BJ (2008). Laboratory Tests and Diagnostic Procedures, 5th ed. St. Louis:
Davis MD, et al. (2013). AARC clinical practice guideline: Blood gas analysis and hemoximetry: 2013. Respiratory Care, 58(10): 1694–1703. DOI: 10.4187/respcare.02786. Accessed March 12, 2014.
Pagana KD, Pagana TJ (2010). Mosby’s Manual of Diagnostic and Laboratory Tests, 4th ed. St. Louis: Mosby Elsevier.
Current as of:
April 9, 2014
E. Gregory Thompson, MD - Internal Medicine & Robert L. Cowie, MB, FCP(SA), MD, MSc, MFOM - Pulmonology
How this information was developed to help you make better health decisions.
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