It is described as a sense of tiredness, lethargy, irritation, or hangover, although the effects can be lessened if a lot of physical activity is undertaken in the first few hours after food consumption.

According to the U.S. National Institutes of Health (NIH), a blood glucose level below 70 mg/dL (3.9 mmol/L) at the time of symptoms followed by relief after eating confirms a diagnosis for reactive hypoglycemia.

[1] Symptoms vary according to individuals' hydration level and sensitivity to the rate and/or magnitude of decline of their blood glucose concentration.

Some researchers suggest that certain people may be more sensitive to the body’s normal release of the hormone epinephrine, which causes many of the symptoms of hypoglycemia.

Stomach bypass surgery or hereditary fructose intolerance are believed to be causes, albeit uncommon, of reactive hypoglycemia.

[13][17] The body requires a relatively constant input of glucose, a sugar produced upon digestion of carbohydrates, for normal functioning.

The “crash” one feels is due to the rapid increase and subsequent decline of blood sugar in the body system as one begins and ceases consumption of high-sugar foods.

[citation needed] Reactive hypoglycemia can usually be relieved by dietary changes:[20] Other tips to prevent sugar crashes include: Low-carbohydrate diet and/or frequent small meals is the first treatment of this condition.

The first important point is to add small meals at the middle of the morning and of the afternoon, when glycemia would start to decrease.

[24] Acute (short-term) low blood sugar symptoms are best treated by consuming small amounts of sweet foods, so as to regain balance in the body's carbohydrate metabolism.