Burping is generally caused by
swallowing air when eating or drinking and subsequently expelling it, so in this case the expelled gas is mainly a mixture of
oxygen. Burps can also be caused by drinking
carbonated beverages, such as
soft drinks in which case the expelled gas is primarily
carbon dioxide from the drink itself. Common diabetes drugs metformin
 and Byetta
 can cause burping, especially at higher doses. This often resolves in a few weeks. Burping combined with other symptoms such as
heartburn may be a sign of an
hiatal hernia, and should be reviewed by a physician.
 Other causes of burping include:
acid reflux disease,
H. pylori, and
Guinness world record for the loudest burp is 109.9
dB, set by Paul Hunn on 23 August 2009.
 This is louder than a
jackhammer at a distance of 1 m (3 ft 3 in).
microgravity environments burping is normally associated with
regurgitation. The valve at the top of the stomach (the
gastroesophageal junction) does not produce a tight seal, and in the absence of gravity, the stomach contents tend to float near this loose seal, making them likely to come up along with the expelled air.
Inability to burp is uncommon, and chest pain caused by dysfunction of the belch reflex is rare.