Insulin test

What is an insulin in blood test?

This test measures the amount of insulin in your blood. Insulin is a hormone that helps move blood sugar, known as glucose, from your bloodstream into your cells. Glucose comes from the foods you eat and drink. It is your body’s main source of energy.

Insulin plays a key role in keeping glucose at the right levels. If glucose levels are too high or too low, it can cause serious health problems. Glucose levels that are not normal are known as:

  • Hyperglycemia, blood glucose levels that are too high. It happens when your body doesn’t make enough insulin. If there’s not enough insulin, glucose can’t get into your cells. It stays in the bloodstream instead.
  • Hypoglycemia, blood glucose levels that are too low. If your body sends too much insulin into the blood, too much glucose will go into your cells. This leaves less in the bloodstream.

Diabetes is the most common cause of abnormal glucose levels. There are two types of diabetes.

  • Type 1 Diabetes. If you have type 1 diabetes, your body makes little or no insulin at all. This can cause hyperglycemia.
  • Type 2 Diabetes. If you have type 2 diabetes, your body may still be able to make insulin, but the cells in your body don’t respond well to insulin and can’t easily take up enough glucose from your blood. This is called insulin resistance.

Insulin resistance often develops before type 2 diabetes. At first, insulin resistance causes the body to make extra insulin, to make up for ineffective insulin. Extra insulin in the bloodstream can cause hypoglycemia. But insulin resistance tends to get worse over time. Eventually, it decreases your body’s ability to make insulin. As insulin levels drop, blood sugar levels rise. If levels don’t return to normal, you may get type 2 diabetes.

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

What is it used for?

An insulin in blood test is most often used to:

  • Find out the cause of hypoglycemia (low blood sugar)
  • Diagnose or monitor insulin resistance
  • Monitor the condition of people with type 2 diabetes
  • Find out if there is a type of tumor on the pancreas, known as an insulinoma. If the tumor has been removed, the test may be used to see if it has been done successfully.

An insulin in blood test is sometimes used along with other tests to help diagnose and monitor type 1 diabetes. These other tests may include glucose and hemoglobin AIC testing.

Why do I need an insulin in blood test?

You may need an insulin in blood test if you have symptoms of hypoglycemia (low blood sugar). These include:

  • Sweating
  • Trembling
  • Irregular heartbeat
  • Confusion
  • Dizziness
  • Blurred vision
  • Extreme hunger

You may also need this test if other tests, such as a blood glucose test, show you have low blood sugar.

What happens during an insulin in blood test?

A health care professional will take a blood sample from a vein in your arm, using a small needle. After the needle is inserted, a small amount of blood will be collected into a test tube or vial. You may feel a little sting when the needle goes in or out.

Will I need to do anything to prepare for the test?

You will probably need to fast (not eat or drink) for eight hours before the test.

Are there any risks to the test?

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.

What do the results mean?

If your insulin levels were too high, it may mean you have:

  • Type 2 diabetes
  • Insulin resistance
  • Hypoglycemia
  • Cushing’s syndrome, a disorder of the adrenal glands. Adrenal glands make hormones that help the body break down fat and protein.
  • An insulinoma (pancreatic tumor)

If insulin levels were too low, it may mean you have:

  • Hyperglycemia (high blood sugar)
  • Type 1 diabetes
  • Pancreatitis, an inflammation of the pancreas