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Proinsulin (Blood)

Does this test have other names?

No.

What is this test?

This blood test measures proinsulin, a building block for insulin.

To turn food into energy, your pancreas makes proinsulin. Proinsulin, in turn, is made into insulin and another protein called C-peptide.

Problems making insulin can lead to diabetes. In type 1 diabetes, your pancreas becomes damaged and has trouble making insulin in your body. In type 2 diabetes, the more common type, your body becomes resistant to the insulin you make.

Your body may also not be able to regulate the amount of insulin you make because of a tumor or a problem with your pancreas.

Measuring proinsulin in your blood can help figure out your risk for type 1 or type 2 diabetes. People with type 1 and type 2 diabetes may have levels of proinsulin that are higher than normal.

Proinsulin levels are also usually high in later stages of type 2 diabetes, and this test can help your healthcare provider decide which treatment is best for you.

Why do I need this test?

You may need this test to see how much proinsulin your body is able to make. This helps your healthcare provider find out your risk for diabetes.

High levels of proinsulin have also been linked to heart and artery disease. Your healthcare provider may want to watch you for heart disease if your proinsulin levels are high.

You may also have this test if your healthcare provider suspects you have hypoglycemia, or low blood sugar. This is when your blood sugar level falls below 50 milligrams per deciliter. This can cause:

  • Uncontrollable shaking

  • Confusion

  • Sweating

  • Heart palpitations

  • Headache

  • Blurry vision

What other tests might I have along with this test?

Your healthcare provider may also order a C-peptide test at the same time as the proinsulin test. If you have C-peptide in your blood, it means your body is making insulin. Checking your C-peptide level helps your healthcare provider figure out if you have type 1 or type 2 diabetes.

If you have low C-peptide levels you may have type 1 diabetes. People with type 2 diabetes usually have normal or high levels of C-peptide.

Your blood may also be tested for:

  • Insulin

  • Sulfonylureas, or certain other medicines used to lower blood sugar in people with type 2 diabetes

  • Blood sugar level after eight hours of fasting, called a fasting glucose test

  • A1C level, which can be used to diagnose diabetes

  • Beta-hydroxybutyrate, a type of ketone found in the blood

What do my test results mean?

Test results may vary depending on your age, gender, health history, the method used for the test, and other things. Your test results may not mean you have a problem. Ask your healthcare provider what your test results mean for you. 

How is this test done?

The test is done with a blood sample. A needle is used to draw blood from a vein in your arm or hand. 

Does this test pose any risks?

Having a blood test with a needle carries some risks. These include bleeding, infection, bruising, and feeling lightheaded. When the needle pricks your arm or hand, you may feel a slight sting or pain. Afterward, the site may be sore. 

What might affect my test results?

Your blood sugar level may affect your results.

How do I prepare for the test?

You may need to fast overnight before you take the test, although the fasting time period before the test varies. Your healthcare provider will give you instructions on how and when to fast. Be sure your healthcare provider knows about all medicines, herbs, vitamins, and supplements you are taking. This includes medicines that don't need a prescription and any illicit drugs you may use.

Medical Reviewers:

  • Fraser, Marianne, MSN, RN
  • Haldeman-Englert, Chad, MD