What is a fasting Insulin Test?
The insulin blood test is also known as the fasting insulin, insulin serum, or total and free insulin test. The fasting insulin test determines the insulin levels in the body after a period of fasting. Insulin is an anabolic hormone secreted by the beta cells of the pancreas and regulates the uptake of glucose, the main source of the body’s energy, from the bloodstream to the cells. Insulin helps maintain glucose within the normal ranges. Too high or too low levels of insulin in the body can be equally harmful and can result in hypoglycemia and hyperglycemia, respectively.
What is the fasting insulin test used for?
The insulin test is used to determine the reason for low blood sugar, monitor insulin resistance, monitor people with type 2 diabetes mellitus, the presence of insulinoma – a tumour on the pancreas, and also to determine the success rate after the removal of the tumour. An insulin test may be used along with blood glucose and glycated haemoglobin (HbA1c) tests to monitor type 1 diabetes mellitus.
Understanding the test results of the fasting insulin test
Always take a healthcare provider’s opinion while interpreting the results of the insulin test and do not self-diagnose. Usually, the insulin and glucose tests are ordered together and interpreted accordingly.
Generally, a high level of insulin can indicate type 2 diabetes mellitus, hypoglycemia (low blood sugar), insulin resistance, Cushing’s syndrome, and pancreatic tumour. Low levels of insulin may be associated with type 1 diabetes mellitus, hyperglycemia (high blood sugar), and inflammation of the pancreas.
The normal levels of insulin in the body are as follows :
- after nearly eight hours of fasting is less than 25 mIU/L,
- 30 minutes after glucose administration is 30-230 mIU/L,
- one hour after glucose ingestion is 18-276 mIU/L,
- two hours after glucose ingestion is 16-166 mIU/L, and
- three hours or more after glucose ingestion is less than 25 mIU/L.
In a healthy person, the insulin level is in proportion with the glucose level.