Low Carbon Dioxide Blood Test

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Symptoms of Low Carbon Dioxide

Certain symptoms may indicate that the concentration of carbon dioxide in the blood is abnormal. Weakness and confusion are the usual signs of an acid-base imbalance. Other indications which might signal to a doctor that there is a problem with the level of carbon dioxide in the blood is prolonged vomiting. Also, general respiratory distress, such as difficulty breathing or shortness of breath, can be signs of an irregular carbon dioxide level in the blood.

Sometimes, the symptoms might not be noticeable. A bicarbonate test is usually given as part of a larger set of blood tests called an electrolyte panel. Usually, individuals receive a low carbon dioxide blood test result during a routine physical examination.

Causes of Low Carbon Dioxide

There are many conditions and diseases which cause a low carbon dioxide blood test result. Addison’s disease, for example, can cause an imbalance in electrolytes. Individuals usually experience dehydration and diarrhea. Another disease which causes low carbon dioxide levels is diabetic ketoacidosis. It is a complication of diabetes that is characterized by high levels of ketones.

Consuming wood alcohol or products that contain ethylene glycol can cause poisoning and result in low carbon dioxide levels. Overdosing on aspirin or other products that contain salicylate and long term starvation can also cause the carbon dioxide level in the blood to be low.

The Bicarbonate Blood Test

Carbon dioxide is found in three forms in the blood - dissolved carbon dioxide, carbonic acid, and bicarbonate. Bicarbonate is the predominant form and is used to determine the level of carbon dioxide in the blood. To measure the bicarbonate level in the blood, a blood sample is taken. A needle is used to draw the blood from a vein, usually in the arm.

The sample is analyzed for bicarbonate, as well as for electrolytes such as sodium, potassium, and chloride. If an acid-base imbalance is suspected, the doctor may also order a blood gas test to determine how well the lungs are exchanging oxygen and carbon dioxide.

Test Results

The normal result of a bicarbonate blood test depends on the age of the individual. For adults, a normal bicarbonate level falls between 23–29 millimoles per liter (mmol/L). Children have a wider range and it falls between 20–28 mmol/L. Infants have the widest range, with normal values falling between 13–22 mmol/L.

There are several factors which may affect the test results including drug interaction. Methicillin, nitrofurantoin, and tetracycline are a few of the medicines which can lower the amount of bicarbonate in the blood. Fludrocortisone, barbiturates, and bicarbonates in contrast increase the amount of bicarbonate in the blood.


1. “Bicarbonate: The Test.” Lab Tests Online. 18 June 2010. 19 Oct. 2010.

2. Curtis, Jeannette. “Carbon Dioxide.” Revolution Health. 9 May 2008. 19 Oct. 2010.