Investigation of Unclear Hypoglycemia with Suspected Insulinoma and Assessment of Insulin Resistance

High Fasting Serum Insulin Levels

Elevated fasting insulin levels are commonly observed in cases of insulin-producing tumors (insulinomas). In such cases, the plasma levels of proinsulin are often elevated as well.

Mild to moderately elevated fasting insulin levels can also be seen in individuals with type II diabetes and other conditions related to metabolic syndrome. Fasting levels in the upper half of the reference range may indicate insulin resistance. The degree of insulin resistance can be assessed through glucose or insulin challenge tests, where insulin and glucose levels are measured after controlled administration of glucose or insulin.

Low or Undetectable Insulin Levels

Low or undetectable serum insulin levels are typical in patients with insulin-dependent diabetes mellitus (type I). To evaluate remaining insulin secretion in patients with diabetes mellitus, testing for C-peptide levels is recommended instead.

Source:

Karolinska University Laboratory - Insulin Testing