Does this test have other names?
Carbon dioxide test, CO2 test
What is this test?
This test measures the amount of bicarbonate, a form of carbon dioxide, in your blood.
Bicarbonate, also known as HCO3, is a byproduct of your body's metabolism. Your blood
brings bicarbonate to your lungs, and then it is exhaled as carbon dioxide. Your kidneys
also help regulate bicarbonate. Bicarbonate is excreted and reabsorbed by your kidneys.
This regulates your body's pH, or acid balance. Bicarbonate also works with sodium,
potassium, and chloride. These substances are called electrolytes. These are often
measured at the same time as bicarbonate.
This test is often part of a comprehensive series of blood tests to check for certain
Why do I need this test?
You may need this test to watch issues that affect pH levels in your blood. You may
also have this test if you have kidney disease, liver failure, or other conditions
related to metabolism.
What other tests might I have along with this test?
You may also need several other tests. These may include:
Arterial blood gas analysis
Electrolyte (sodium, potassium, and chloride) testing as part of a basic or comprehensive
Urine pH testing
Anion gap blood testing
What do my test results mean?
Test results may vary depending on your age, gender, health history, the method used
for the test, and other things. Your test results may not mean you have a problem.
Ask your healthcare provider what your test results mean for you.
Results are given in milliequivalents per liter (mEq/L) or millimoles per L (mmol/L).
Normal bicarbonate levels are:
A high level of bicarbonate in your blood can be from metabolic alkalosis, a condition
that causes a pH increase in tissue. Metabolic alkalosis can happen from a loss of
acid from your body, such as through vomiting and dehydration. It may also be related
to conditions including anorexia and chronic obstructive pulmonary disease.
A low level of bicarbonate in your blood may cause a condition called metabolic acidosis,
or too much acid in the body. A wide range of conditions, including diarrhea, kidney
disease, and liver failure, can cause metabolic acidosis.
How is this test done?
The test is done with a blood sample. A needle is used to draw blood from a vein in
your arm or hand.
Does this test pose any risks?
Having a blood test with a needle carries some risks. These include bleeding, infection,
bruising, and feeling lightheaded. When the needle pricks your arm or hand, you may
feel a slight sting or pain. Afterward, the site may be sore.
What might affect my test results?
Eating acidic fruits could affect your results. Medicines that may raise your levels
Medicines that may lower your levels include:
How do I get ready for this test?
You don't need to get ready for this test. Tell your healthcare provider about all
medicines, herbs, vitamins, and supplements you are taking. This includes medicines
that don't need a prescription and any illegal drugs you may use.