A hangover is typically experienced the next morning, after a night of heavy drinking. It refers to the unpleasant physiological consequences of excessive consumption of alcoholic beverages.  The symptoms of a hangover usually include one or more of the following: headache sensitivity to light and sound nausea diarrhea increased heart rate and blood pressure fatigue lethargy anxiety sometimes, depression thirst Hypoglycemia (abnormal glucose levels), dehydration, acetaldehyde (product of alcohol metabolism)