Insulin in Blood

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.

Why this test is done

You may need an insulin in blood test if you:

• Had a blood glucose test that showed you have low blood glucose levels.
• Have symptoms of hypoglycemia (low blood glucose). Symptoms of mild to moderate hypoglycemia include:
• Sweating
• Feeling shaky or jittery
• Arrythmia (a problem with the rate or rhythm of your heartbeat)
• Confusion
• Dizziness
• Headache
• Hunger

Severe hypoglycemia can cause fainting and seizures. This serious condition needs medical treatment right way.

• Have insulin resistance or have a high risk for developing it. Your risk for insulin resistance is higher if you have:
• Prediabetes
• Type 2 diabetes
• Polycystic ovary syndrome (PCOS)
• Heart disease
• Acanthosis nigricans (dark, thick, velvety skin around the neck or armpits)
• Had surgery on your pancreas:
• To transplant the part of the pancreas that makes insulin (islet cell transplantation). You may need insulin testing to see if the transplant is working properly.
• To remove an insulinoma. This is a tumor in the pancreas that makes too much insulin and causes low blood glucose. After surgery you may need insulin testing to check whether any tumor tissue is left and to see if the tumor has come back. Insulinomas are uncommon and usually aren't cancer.

How to prepare

Your health care provider will tell you how to prepare for an insulin in blood test. You will probably need to fast (not eat or drink) for 8 to 12 hours before the test. 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.

But don't stop taking any medicines without talking with your provider first.

Sample type

Blood

Other names for this test

fasting insulin, insulin serum, total and free insulin