Hypoglycemic disorders cause symptoms primarily in the postprandial or fasting states, and rarely in a chaotic fashion unrelated to food ingestion or deprivation. Some disorders that cause hypoglycemia predominantly in the postprandial state are the noninsulinoma pancreatogenous hypoglycemia syndrome (NIPHS), postgastric bypass hypoglycemia, and insulin autoimmune hypoglycemia (table 1).
The diagnosis, evaluation, and management of patients with hypoglycemic symptoms that predominantly occur in the postprandial state will be reviewed here. Other causes of hypoglycemia and the diagnostic approach to hypoglycemia are discussed separately. (See "Hypoglycemia in adults: Clinical manifestations, definition, and causes" and "Hypoglycemia in adults without diabetes mellitus: Diagnostic approach".)
Postprandial (reactive) hypoglycemia — Postprandial or reactive hypoglycemia is a descriptor of the timing of hypoglycemia (within four hours after meals) and is not a diagnosis per se. Its presence requires an evaluation to determine the cause of hypoglycemia.
The term reactive hypoglycemia is often erroneously used to describe a functional or idiopathic disorder observed in patients with nondescript postprandial symptoms and no biochemical evidence of hypoglycemia after ingestion of a high carbohydrate meal and with resolution of symptoms after dietary modification [1-3] (see 'Postprandial syndrome' below). The danger in considering postprandial (reactive) hypoglycemia as a disease itself, rather than a descriptor of the timing of hypoglycemia, is the failure to search for the underlying cause of the hypoglycemia.
Postprandial syndrome — In the remote past, patients with symptoms suggestive of increased sympathetic activity (anxiety, weakness, tremor, perspiration, or palpitations) occurring after meals were considered to have functional hyperinsulinism or functional hypoglycemia, as a reaction to the ingestion of food. The diagnosis was based upon reproduction of the patient's hypoglycemia symptoms in association with a blood glucose value of <50 mg/dL (2.8 mmol/L) after an oral glucose tolerance test (OGTT) . However, the value of an OGTT in diagnosing reactive hypoglycemia has been discredited based upon the following observations: