Insulin Fasting Test

An Insulin Fasting test measures the level of insulin in your blood after a fasting period of 8-12 hours. It is done when symptoms like increased thirst or urination, appetite changes, weakness, weight changes, tingling or numbness in the hands or legs, etc. are experienced by an individual.

What is an insulin in blood test?

An insulin in blood test measures the amount of insulin in a sample of your blood. Insulin is a hormone that your pancreas makes. It helps move blood glucose (blood sugar) from your bloodstream into your cells where it's used for energy. Glucose comes from many foods you eat. It's your body's main source of energy.

Normally, insulin and blood glucose levels rise and fall together:

• Blood glucose levels increase after you eat.
• When blood glucose rises, your pancreas releases more insulin into your blood.
• The insulin lets glucose get into your cells, which lowers your blood glucose level.
• When your blood glucose level returns to a range that's normal for you, your insulin levels decrease, too.

Serious problems can develop if your pancreas doesn't make the right amount of insulin at the right time. For example:

• If your pancreas makes too much insulin, you may have too little glucose in your blood. This is called hypoglycemia. If blood glucose levels drop to a very low level (severe hypoglycemia), your brain cells may not get enough glucose to work properly. This is a serious condition that needs medical treatment right away.
• If your pancreas makes too little insulin, glucose can't get into your cells from your blood. The glucose builds up in your bloodstream until your blood glucose level is too high. This is called hyperglycemia. If your blood glucose levels stay high over time, you could develop type 2 diabetes, which can cause serious complications in your eyes, heart, and other parts of your body.

If you have signs or symptoms of a health condition related to insulin, an insulin in blood test can help check how much insulin your pancreas is making.

Other names: fasting insulin, insulin serum, total and free insulin

What is it used for?

An insulin in blood test may be used with other tests to help:

• Find out the cause of hypoglycemia (low blood glucose). This is the main reason for doing insulin testing.
• Diagnose insulin resistance. With insulin resistance, your cells don't respond well to insulin and can't easily take in glucose from your blood. Your pancreas may make more insulin to help glucose get into your cells. This can keep your blood glucose in a healthy range for a while. But over time, your pancreas may wear out and stop making enough insulin. This can lead to prediabetes, which means your blood glucose levels are higher-than-normal, but not high enough to be diabetes. If blood glucose levels keep increasing, you can develop type 2 diabetes.
• Guide treatment decisions for type 2 diabetes. An insulin test may be used to decide if a person with type 2 diabetes needs to take insulin as part of their diabetes treatment.
• To monitor how well pancreatic islet cell transplantation surgery is working. This surgery is used in people who have type 1 diabetes. Type 1 diabetes is an autoimmune disease that destroys the special islet cells in the pancreas that make insulin.