Hyperinsulinism can be associated with several types of medical problems, which can be roughly divided into two broad and largely non-overlapping categories: those tending toward reduced sensitivity to insulin and high blood glucose levels (hyperglycemia), and those tending toward excessive insulin secretion and low glucose levels (hypoglycemia).

[1] In contrast, hyperinsulinemic hypoglycemia can produce any of the entire range of hypoglycemic symptoms, from shakiness and weakness, to seizures or coma.

[2] Although many factors influence insulin secretion, the most important control is the amount of glucose moving from the blood into the beta cells of the pancreas.

In normal children and adults, insulin secretion should be minimal when blood glucose levels fall below 70 mg/dL (3.9 mM).

[citation needed] That spontaneous hyperinsulinism might be a cause of symptomatic hypoglycemia was first proposed by Seale Harris, MD, 1924, in Journal of the American Medical Association.