Low carbon dioxide generally refers to low partial pressure of carbon dioxide. The main causes of low partial pressure of carbon dioxide are hyperventilation, metabolic acidosis and central nervous system dysfunction. 1. Hyperventilation: Carbon dioxide partial pressure is one of the common indicators of arterial blood gas analysis, which refers to the pressure generated by carbon dioxide molecules dissolved in the blood. When the body is in a state of emotional excitement, it will lead to large mouth breathing, and a large amount of carbon dioxide is discharged from the body, resulting in a decrease in the partial pressure of carbon dioxide. 2. Metabolic acidosis: When metabolic acidosis occurs, the body needs compensatory acid excretion, which can lead to a compensatory decrease of carbon dioxide in the body. 3. Central nervous system dysfunction: when the respiratory center is damaged, it can lead to abnormal respiration and promote the discharge of carbon dioxide in the body. It is recommended to go to a specialized hospital to identify the cause of the disease and follow the doctor’s instructions.