Insulin testing may be used to help:
• Diagnose an insulinoma, verify that removal of the tumor has been successful, and/or to monitor for recurrence
• Determine 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. Both tests may be ordered to evaluate how much insulin in the blood is made by the body and how much is from outside (exogenous) sources such as insulin injections. The test for insulin measures insulin from both sources while the C-peptide test reflects insulin produced by 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 of the transplant.
Insulin levels are also sometimes used in conjunction with the glucose tolerance test (GTT). In this situation, blood glucose and insulin levels are measured at pre-established time intervals to evaluate insulin resistance.
Insulin levels are most frequently ordered following a low glucose test result and/or when someone has acute or chronic symptoms of low blood glucose (hypoglycemia) caused by, for example, an insulinoma. Symptoms of hypoglycemia may include:
• Blurred vision
In serious cases, seizures and loss of consciousness
These symptoms may indicate low blood glucose but may also be seen with other conditions.
An insulin test may also be done when an individual has or is suspected of having insulin resistance. This may include people with type 2 diabetes, polycystic ovarian syndrome (PCOS), prediabetes or heart disease, or metabolic syndrome.
For more information on this test, visit labtestsonline.org
Fast for 8 hours before blood is collected