Hyperventilation is breathing that is deeper and more rapid than normal, which causes the amount of carbon dioxide (CO2) in the blood to drop too low. This may result in lightheadedness, a rapid heartbeat, shortness of breath, numbness or tingling in the hands or feet, anxiety, fainting, and sore chest muscles.

Some causes of hyperventilation include extreme anxiety, asthma, emphysema, head injury, fever, exposure to altitude above 6000 ft (2000 m), and some medications.

In many cases, hyperventilation can be controlled with home treatment, such as focusing on proper breathing techniques.