Hyperinsulinemia is the presence of elevated levels of insulin in the bloodstream. Insulin is the hormone normally produced by the pancreas to help regulate blood sugar levels. When insulin levels are too high, this is most often indicative of insulin resistance, a state in which the body does not respond well to insulin and the body compensates by making more. Insulin resistance may lead to the development of type 2 diabetes. Hyperinsulinemia usually does not cause any signs or symptoms. Rare causes of hyperinsulinemia include tumors that produce insulin (insulinoma) or excess numbers of insulin-producing cells in the pancreas (nesidioblastosis).
Jameson, J. Larry, et al. Harrison's Principles of Internal Medicine, 20th Ed. New York: McGraw-Hill Education, 2018.