A
sugar crash or
glucose crash is the fatigue after consuming a large quantity of
carbohydrates, also known as
reactive hypoglycemia. It is variously described as a sense of tiredness, lethargy, irritation, or hangover, although the effects can be less if one has undertaken a lot of physical activity within the next few hours after consumption. The alleged mechanism for the feeling of a crash is correlated with an abnormally rapid rise in
blood glucose after eating. This normally leads to
insulin secretion (known as an
insulin spike), which in turn initiates rapid glucose uptake by tissues either accumulating it as
glycogen or utilizing it for energy production. The consequent fall in blood glucose is indicated as the reason for the "sugar crash".