The insulin-glucose ratio corrects for technical problems in the insulin assay. Because insulin secretion in healthy beta-cells is reduced to basal levels with hypoglycemia, insulin would not be detectable at glucose levels of about 30 mg/dL. It is used in the diagnosis of insulinoma, where secretion of insulin is independent of glucose levels. The change in the ratio during more prolonged fasting gives a better diagnostic separation between patients with inappropriate islet cell secretion from normal subjects.
