You have several forms of hemoglobin in your red blood cells. The most abundant is hemoglobin A, or alpha-hemoglobin. It accounts for 90% or more of the hemoglobin in adults. Most of your hemoglobin A is subtype A1. When hemoglobin A1 absorbs glucose, it becomes glycated hemoglobin, or hemoglobin A1C. The more glucose there is in the blood, the more hemoglobin A1C is formed. The level of hemoglobin A1C can be measured with a blood test, as explained by the American Diabetes Association.
Urine Tests
Before tests were developed for blood glucose --- a blood sugar that is used by your body --- sugar testing was done with urine. In the distant past, physicians would even taste urine to see if they could detect sweetness. The chemical urine tests are accurate if done and read correctly, but the blood glucose must be quite high for it to show up in the urine several hours later. Sugar in the urine is often a sign that diabetes is present and a high positive result may indicate that it is out of control.
Blood Glucose Test
The blood glucose tests reflect a current blood sugar level. The blood glucose level fluctuates from hour to hour and from day to day. To get a true fasting level, you have to fast for at least eight hours before the test. Then, a high blood sugar level must often be followed by a glucose tolerance test to diagnose diabetes accurately. The blood glucose test is still used for diagnosis but is often replaced now with the A1C test. The simple finger-stick blood glucose test is useful for monitoring through the day.
Hemoglobin A1C Test
A red blood cell lives for about three months. During these months, some of the hemoglobin A1 becomes glycated when there is any extra sugar in the blood. It stays that way until the cell itself wears out and is destroyed by the spleen. During those three months, you may have had high blood sugar at some times and normal or low levels at others. If your blood is tested for the percent of hemoglobin A1C present, it reflects your average blood sugar over the past few months. This is a much more useful test for diagnosing diabetes as well as for checking your progress in controlling it.
Test Results
According to information at Mayo Clinic.com, a diagnostic test level of hemoglobin A1C between 4.5 and 6 percent indicates normal processing of blood sugar and no diabetes. If the level is 6.5 percent and a follow up test is at or above this level, you are considered diabetic. For diabetics, a goal level may be 7 or below, which indicates good control of blood sugar for those patients. A level of 9 percent or above indicates poor control of diabetes.
Testing
You may have an A1C test done if your fasting blood glucose is high or as a monitoring tool if you are diabetic. This is usually done at a doctor's office, but there is now a home test available. You may test your blood sugar several times a day, but the A1C test is only done every six months or as your doctor advises. If you decide to test at home, choose a quiet time and be sure to follow the instructions carefully. Let your doctor and diabetes counselors know the results each time you test the hemoglobin A1C, and do be sure to call right away if the results are out of range for you.
References
- Information Center for Sickle Cell and Thalassemic Disorders: Hemoglobinopathies (Hemoglobin Disorders); revised April 17, 2002
- American Diabetes Association: Living With Diabetes: A1C
- A Historical Perspective of the Diagnosis of Diabetes; Mark Kirchhof, BSc, Nooreen Popat, BSc, Janet Malowany, BHSc; University of Western Ontario; 2008
- MayoClinic.com: A1C test: Results
