Glycohemoglobin (GHb)

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Test Overview

Glycohemoglobin is a blood test that checks the amount of sugar (glucose) bound to hemoglobin. Normally, only a small percentage of hemoglobin in the blood (4% to 6%) has glucose bound to it. People who have diabetes or other conditions that increase their blood glucose levels have more glycohemoglobin than normal.

The glycohemoglobin A1c test checks the long-term control of blood glucose levels in people with diabetes. Most doctors think the glycohemoglobin A1c level is the best way to check how well a person is controlling his or her diabetes.

A home blood glucose test measures the level of blood glucose only at that moment. Blood glucose levels change during the day because of diet, exercise, and the level of insulin in the blood.

It is useful for a diabetic to have information about the long-term control of blood sugar levels. The glycohemoglobin test is one blood sample every 3 to 4 months, and the test does not change with any recent changes in diet, exercise, or medicines.

Glucose binds to hemoglobin in red blood cells at a steady rate. Since red blood cells last 3 to 4 months, the glycohemoglobin A1c test shows how much glucose is in the plasma part of blood. This test shows how well your diabetes has been controlled in the last 2 to 3 months and whether your diabetes medicine needs to be changed.

The A1c level can also help your doctor see how big your risk is of developing problems from diabetes, such as kidney failure, vision problems, and leg or foot numbness. The lower your A1c level, the lower your chance for problems.

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Last updated:	June 13, 2006
Author:	Jan Nissl, RN, BS
Reviewed By:	Caroline S. Rhoads, MD - Internal Medicine, David C.W. Lau, MD, PhD, FRCPC - Endocrinology & Metabolism
Editors:	Susan Van Houten, RN, BSN, MBA, Tracy Landauer