What Causes Low Co2 Levels?

Low carbon dioxide (CO2) in the body, or hypocapnia, causes blood to be less acidic. This condition is caused by hyperventilation, or excessive ventilation. It leads to a loss of carbon dioxide from the blood. It can be done on purpose, but mostly it is involuntary. CO2 is usually eliminated from the body rather quickly. The majority of it is transported through the blood as bicarbonate, only to be transformed back into CO2 once it has reached the lungs. This process helps to regulate the acid/alkaline balance in the body.

Any uncontrolled disease or metabolic disorder that causes an increase in respiration can cause a decrease in carbon dioxide in the blood.


Sometimes an increase in hormones can cause an increase in respiration. Progesterone levels increase dramatically during pregnancy. This hormone causes stimulation of the respiratory center and can lead to a decrease in CO2.

Congestive Heart Failure

Effects of Serotonin on the Body

Learn More

Hyperventilation occurs in patients suffering from congestive heart failure during rest, sleep and exercise. This low cardiac output and fast breathing leads to low CO2 levels. Congestive heart failure results when disease weakens the heart so that the pumping action normally done can no longer meet the needs of the body.


Hyperthyroidism causes hyperventilation by increasing ventilation hormones. It can significantly increase the body's metabolism, causing sudden weight loss, irregular heartbeat and sweating. These symptoms cease and everything returns to normal once treatment begins.

Chronic Liver Disease

Homeostatic Regulation of Blood Pressure

Learn More

Although this is highly hypothesized, hyperventilation due to liver disease is thought to be caused by increased levels of progesterone, ammonia, peptides and glutamine. These all increase respiration. The degree of hyperventilation correlates with the severity of the disease. The University of Maryland Medical Center describes liver disease as cirrhosis of the liver and fibrosis of the liver. Over time, the destruction of the liver tissue signifies liver disease.

Hyperventilation Syndrome

First described in 1935 by Christie, hyperventilation syndrome is caused by stress and anxiety. Acting on behavioral respiratory control system, both of these factors cause hyperventilation. During sleep, when the behavior control system is inactive, hyperventilation stops. A diagnosis of hyperventilation syndrome is only made after ruling out every other medical condition first.