Fasting Insulin Test: What Do the Test Results Tell?

Fasting insulin test, is used to help evaluate insulin production in the pancreas; to help diagnose the presence of an insulin-producing tumor in the islet cells of the pancreas (insulinoma), to help determine the cause of low blood glucose (hypoglycemia), to help identify insulin resistance, or to help determine when a type 2 diabetic might need to start taking insulin to supplement oral medications.

Results Reference:

Disorder Fasting insulin level Fasting glucose level
none normal normal
insulin resistance high normal or somewhat elevated
not enough insulin produced by the beta cells (may be seen in insulinomas, Cushing syndrome, excess administration of exogenous insulin, etc.) normal, or high low

What else can I know from the test results?

  • Elevated insulin levels are seen with: acromegaly, Cushing syndrome, use of drugs such as corticosteroids, levodopa, oral contraceptives, fructose or galactose intolerance, insulinomas, obesity, insulin resistance (often appearing in type 2 diabetes), acanthosis nigricans, and metabolic syndrome.
  • Decreased insulin levels are seen with: diabetes, hypopituitarism, pancreatic diseases such as chronic pancreatitis (including cystic fibrosis) and pancreatic cancer.


Keywords: Fasting Insulin, Insulin, Insulin serum

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