Hypoglycemia occurs when blood glucose levels dip below normal ranges (i.e., less than 50 milligrams of glucose per deciliter of blood, or mg/dL).[1][2] Reactive hypoglycemia (RH) is a subtype of hypoglycemia which is often defined by a dip in blood glucose that occurs 2–5 hours after a meal (postprandial). Since RH is not fully understood, its definition varies and sometimes also includes a dysfunctional response to insulin and/or to the consumption of specific foods. RH may occur in both individuals with and without diabetes and may lead to insulin resistance.[3][4][5] [6][7][8][9][10] RH has been categorized into at least three forms, which depend on how quickly symptoms appear after eating: RH that occurs 2–3 hours post meal is considered alimentary, 3–4 hours after a meal is idiopathic, and longer than 4 hours post meal is called late RH.[6][7]
What is reactive hypoglycemia?
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•Last Updated: May 16, 2025
Reactive hypoglycemia is a subtype of hypoglycemia characterized by a drop in blood glucose levels that occurs 2 to 5 hours after eating, and varying definitions may include dysfunctional insulin responses. It can affect both people with and without diabetes and is categorized into 3 forms based on the timing of symptoms after meals.