Blood carbon dioxide usually indicates the total amount of carbon dioxide from bicarbonate and carbonic acid, so low blood carbon dioxide suggests reduced carbon dioxide binding. It is usually due to metabolic acidosis, respiratory alkalosis and hypoxemia. 1. Metabolic acidosis: excessive loss of alkaline substances due to severe diarrhea, etc., leading to water electrolyte disorders, will lead to metabolic acidosis, which will damage the respiratory system of the human body, leading to excessive carbon dioxide exhalation, resulting in low carbon dioxide levels in the blood. 2. Respiratory alkalosis: mainly caused by respiratory diseases resulting in hyperventilation, patients will have shortness of breath, and if the symptoms persist for a long time, it may lead to excessive exhalation of carbon dioxide, resulting in low carbon dioxide in the blood. 3. Hypoxemia: due to the low partial pressure of arterial oxygen, patients with hypoxemia can reflexively stimulate the respiratory center, enhance respiratory movement, causing the respiratory rate to increase, which can also lead to low carbon dioxide content in the blood if it is not dealt with in a timely manner. If the patient’s blood carbon dioxide level is low, it is recommended to go to the hospital in time to improve the relevant examinations, and give appropriate treatment in combination with the cause of the disease.