Reactive hypoglycemia

Reactive hypoglycemia
Other names	Postprandial hypoglycemia, sugar crash
A typical recommendation: Half the plate is filled with high-fiber vegetables, and the rest is divided between tuna fish and a single serving of whole grain ramen noodles.
Symptoms	Clumsiness, difficulty talking, confusion, loss of consciousness, and other symptoms related to hypoglycemia
Usual onset	Within 4 hours of a high carbohydrate meal
Causes	Gastric bypass surgery, over-secretion of insulin
Diagnostic method	Whipple criteria, blood glucose test during spontaneous occurrence of symptoms, HbA1c blood test, 6-hour glucose tolerance test
Differential diagnosis	Alimentary hypoglycemia, factitious hypoglycemia, insulin autoimmune hypoglycemia, noninsulinoma pancreatogenous hypoglycemia syndrome, insulinoma, hereditary fructose intolerance
Prevention	Low-carbohydrate diet, frequent small meals

Reactive hypoglycemia, postprandial hypoglycemia, or sugar crash is a term describing recurrent episodes of symptomatic hypoglycemia occurring within four hours^[1] after a high carbohydrate meal in people with and without diabetes.^[2] The term is not necessarily a diagnosis since it requires an evaluation to determine the cause of the hypoglycemia.^[3]

The condition is related to homeostatic systems used by the body to control the blood sugar level. 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.

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 storing it as glycogen or fat, or using it for energy production. The consequent fall in blood glucose is indicated as the reason for the "sugar crash".^[4] Another cause might be hysteresis effect of insulin action, i.e., the effect of insulin is still prominent even if both plasma glucose and insulin levels were already low, causing a plasma glucose level eventually much lower than the baseline level.^[5]

Sugar crashes are not to be confused with the after-effects of consuming large amounts of protein, which produces fatigue akin to a sugar crash, but are instead the result of the body prioritising the digestion of ingested food.^[6]

The prevalence of this condition is difficult to ascertain because a number of stricter or looser definitions have been used. It is recommended that the term reactive hypoglycemia be reserved for the pattern of postprandial hypoglycemia which meets the Whipple criteria (symptoms correspond to measurably low glucose and are relieved by raising the glucose), and that the term idiopathic postprandial syndrome be used for similar patterns of symptoms where abnormally low glucose levels at the time of symptoms cannot be documented.

To assist in diagnosis, a doctor may order an HbA1c test, which measures the blood sugar average over the two or three months before the test. The more specific 6-hour glucose tolerance test can be used to chart changes in the patient's blood sugar levels before ingestion of a special glucose drink and at regular intervals during the six hours following to see if an unusual rise or drop in blood glucose levels occurs.

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]