What Causes High Levels of Co2 in Blood?

Hypercapnia is a condition in which high carbon dioxide (CO2) levels are retained in the blood. It can be extremely dangerous, leading to death, and there are numerous things that can lead to a high CO2 presence in the blood.


Hypoventilation occurs when breathing is not adequate to take in enough oxygen and eliminate enough carbon dioxide through exhalation. Because exhalation is not releasing CO2 from the body at a strong enough rate, it builds up in the blood, possibly to toxic and even fatal levels.

Lung Disease

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Lung disease is another cause of high levels of CO2 in the blood. Reduced alveolar and overall lung capacity causes a reduced ability to both inhale enough oxygen and exhale enough carbon dioxide, leading to hypercapnia.

Loss of Consciousness

With diminished consciousness comes diminished breathing, and this can lead to hypercapnia. This is often the case during a drug overdose, where consuming too much of a specific substance reduces faculties enough to cause a loss of consciousness, which can lead to hypercapnia.

Atmospheric Inhalation

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In addition to physiological causes, increased inhalation of carbon dioxide from the environment can lead quickly to hypercapnia and death. This is especially true in instances of fire, where the oxygen in the air is consumed and carbon dioxide is abundant.


Sea divers often breathe inadequately while diving, which can lead to hypercapnia. This can be exasperated by poor or malfunctioning equipment required to remove CO2 from the breathing apparatus. Additionally, divers can overexert themselves, also leading to hypercapnia.