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Latest Edit: Hector 2014-03-24 (EDT)

See Also Lab Tests

The C-peptide test, also known as the insulin C-peptide test is used to monitor insulin production by the beta cells in the pancreas. This test can help to determine the cause of hypoglycemia.[1], [2]


  • This test measures the amount of C-peptide; a substance that is produced when proinsulin, an inactive molecule, splits apart to form C-peptide and insulin. C-peptide can be found in a blood or urine sample.
  • C-peptide is produced at the same rate as insulin, thereby making it a useful marker of insulin production.
  • This test may be used to help evaluate the production of insulin made by the body.

Patient Preparation

  • Ask your doctor if fasting is required before having the test performed.

Clinical Implications

High levels indicate:

  • High levels of endogenous insulin production
  • Insulinoma
  • Hypokalemia
  • Pregnancy
  • Cushing's syndrome
  • Renal failure

Low levels indicate:

  • Low levels of endogenous insulin production
  • Suppression by exogenous insulin

Associated Tests


  1. Pagana Kathleen D, Pagana Timothy J (2006) Mosby's Manual of Diagnostic and Laboratory Tests, Mosby.
  2. Weatherby Dicken, Ferguson Scott (2002) Blood Chemistry and CBC Analysis: Clinical Laboratory Testing from a Functional Perspective, Bear Mountain.