Insulin in Blood
Reviewed
Also called: Fasting Insulin, Insulin Serum, Total and Free Insulin
This test measures the amount of insulin in a sample of your blood. Insulin is a hormone that helps move blood glucose into your cells for energy. The test is often used to find the cause of low blood glucose (hypoglycemia), diagnose insulin resistance, guide treatment for type 2 diabetes, or monitor how well pancreatic islet cell transplantation surgery is working.
Specimen: Blood
Urgent safety information
Severe hypoglycemia can cause fainting and seizures and needs medical treatment right away.
Why this test may be ordered
- To help find out the cause of hypoglycemia (low blood glucose).
- To diagnose insulin resistance.
- To guide treatment decisions for type 2 diabetes.
- To monitor how well pancreatic islet cell transplantation surgery is working.
- To check after surgery to remove an insulinoma.
Preparation and collection
Your health care provider will tell you how to prepare. You will probably need to fast (not eat or drink) for 8 to 12 hours before the test.
A health care professional will take a blood sample from a vein in your arm, using a small needle.
There is very little risk to having a blood test. You may have slight pain or bruising at the spot where the needle was put in, but most symptoms go away quickly.
Understanding results
To understand what your insulin test results mean, your provider will consider your medical history and results of other tests, including a blood glucose test.
- High insulin with normal or slightly high blood glucose: High insulin with normal or slightly high blood glucose may mean you have insulin resistance. Limitation: Results should be interpreted by your healthcare professional based on your individual situation. Next step: Your provider may check for insulin resistance or other conditions.
- High or normal insulin with low blood glucose: High or normal insulin with low blood glucose may mean you have hypoglycemia from too much insulin. Limitation: Severe hypoglycemia can cause fainting and seizures and needs medical treatment right away. Next step: Your provider may look for causes such as a pancreatic tumor (insulinoma), Cushing's syndrome, or taking too much insulin for diabetes.
- Low insulin with high blood glucose: Low insulin with high blood glucose may mean your pancreas can't make enough insulin. Limitation: Results should be interpreted by your healthcare professional based on your individual situation. Next step: Your provider may consider type 1 diabetes or pancreatitis as possible causes.
- If you take biotin supplements (vitamin B7), or supplements that include biotin, you'll need to stop taking them for at least a day before your test.
- You will probably need to fast (not eat or drink) for 8 to 12 hours before the test.
What to do next
Ask your provider to explain what your test results say about your health and what follow-up steps are needed.
- What do my insulin and blood glucose results mean together?
- Do I need any other tests, such as a C-peptide test?
- What is my risk for insulin resistance or diabetes?