Insulin testing may be used to help diagnose an insulinoma, and diagnose the cause of hypoglycemia in an individual with signs and symptoms Identify insulin resistance - Monitor the amount of insulin produced by the beta cells in the pancreas (endogenous); in this case, a C-peptide test may also be done. Insulin and C-peptide are produced by the body at the same rate as part of the conversion of proinsulin to insulin in the pancreas. - Determine when a type 2 diabetic might need to start taking insulin to supplement oral medications - Determine and monitor the success of an islet cell transplant intended to restore the ability to make insulin, by measuring the insulin-producing capacity.Insulin is produced by beta cells of the pancreas. It leads to Type 1 diabetes caused by Insulin deficiency & Type 2 diabetes caused by insulin resistance. This assay is useful in the management of Diabetes. It is also used for diagnosing Insulinoma when used in conjunction with Proinsulin and C-peptide measurement.