Hemoglobin and Diabetes - How are They Related?

red blood cells
Hemoglobin is a protein in red blood cells that carries oxygen from the lungs to the tissues in the body. STEVE GSCHMEISSNER/Science Photo Library/Getty Images

Hemoglobin and diabetes have an ongoing relationship. Glucose collects on hemoglobin in your red blood cells and stays there for up to three months The amount of glucose attached to your hemoglobin is tested in the hemoglobin A1c test and reported as the EAG number. How are hemoglobin and diabetes related?

What is Hemoglobin?

Hemoglobin is a protein molecule in your red blood cells that carries oxygen from your lungs to all parts of your body.

Nearly all of the oxygen in your blood is carried on hemoglobin, so it is vitally important. It contains iron and it is what makes red blood cells red in color. When you have "iron-poor blood" it is due to not having enough hemoglobin in your red cells.

How is Hemoglobin Used to Test for Diabetes?

When you eat, your body pulls the glucose or sugar from those foods and uses it for energy. It eventually ends up in your bloodstream so that it can be carried to all parts of your body. Some of the sugar that ends up in your bloodstream attaches to the hemoglobin on your red blood cells and stays there for up to three months. Most of your red cells are recycled after four months, so your cells show only the past three month's history.

If you have elevated levels of sugar in your blood, as many people with diabetes do, then more of that sugar will attach to your red blood cells. The higher the concentration of sugar in your blood, the more sugar attaches to your hemoglobin.

Hemoglobin A1c Test and Diabetes

Daily blood glucose testing is critically important in the overall management of diabetes. But, these tests give only a snapshot of the level of glucose in the bloodstream at the time of the test. One hour later, the result may be different. A test called hemoglobin A1c gives a longer view of glucose levels by measuring how much glucose has attached to hemoglobin over the life of the red blood cell, which is about three months.

It is considered the gold standard test to understand longer-term glucose levels in the blood and is recommended by the American Diabetes Association. It is also used as a screening test for diabetes.

Hemoglobin Variants Affect the A1C Test

The A1c test is not accurate in people with variant forms of hemoglobin. People of African, Mediterranean or Southeast Asian heritage may inherit these variations of hemoglobin. These include hemoglobin S, seen in people with sickle cell trait, and hemoglobin C or E. Hemoglobin F is seen during pregnancy, both in the fetus and sometimes in the pregnant woman. Having these forms of hemoglobin do not mean you have any health problems, but they can cause false results with the A1C test. Your health care provider can do a blood test to determine if you have a hemoglobin variant.

Consequences of high blood sugar

Studies have conclusively shown that elevated glucose over a long period of time puts a person with diabetes at higher risk for many health problems that involve the:

  • heart
  • eyes
  • Kidneys
  • Feet
  • Nerves
  • Blood vessels


National Center for Biotechnology Information. Type 1 Diabetes

"For People of African, Mediterranean, or Southeast Asian Heritage: Important Information about Diabetes Blood Tests," National Institute of Diabetes and Digestive and Kidney Diseases, October, 2011.

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