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Friday, December 6, 2013
Normal A1c: How Can a Person Have Diabetes?
If the results of the A1C test are never over 6, could a person still have Type 2 diabetes?
The questioner is asking about hemoglobin A1c, a test of long-term blood sugar control and the diagnosis of diabetes. The normal range for hemoglobin A1c is generally in the 4-6% range (in our hospital normal for hemoglobin A1c is 4.7-6.4%). So implicit in the question is, "If the hemoglobin A1c is normal, how can the person have diabetes?" The criteria for making a diagnosis of diabetes are based on blood glucose (sugar) results. Given the nature of the disease process resulting in diabetes, once the person has had a set of abnormal test results (except for the diagnosis of gestational diabetes which is diabetes that comes on during a pregnancy and goes away at the end of pregnancy), they carry the diagnosis of diabetes from that time forward even if they do a great job of controlling the blood sugars. So that essentially forms the basis for the answer to this question: A person with type 2 diabetes can do an excellent job of controlling their blood sugars and keep the Hemoglobin A1c at or below 6 but they still have diabetes.
Some people have talked about the possibility of using Hemoglobin A1c to make a diagnosis of diabetes. That is not currently accepted by the American Diabetes Association, in large part for the reasons outlined here. But it is possible that someday a consensus may be reached that if a person reaches a certain markedly elevated level of Hemoglobin A1c, that could provide a basis for making a diabetes diagnosis. My own research addresses the question of what factors can make a given individual's Hemoglobin A1c higher or lower than one might expect from their blood sugars. There can be such mismatches fairly commonly and that would be a concern in using Hemoglobin A1c for diagnosis.
The three NetWellness parent institutions, the University of Cincinnati, Case Western Reserve University and the Ohio State University are each participating in a national research study called the ACCORD (Action to Control Cardiovascular Risk in Diabetes) Trial which tests whether reducing the Hemoglobin A1c below 6 in people with diabetes reduces their risk of heart attacks and strokes. It is possible that even though the person still has diabetes at this Hemoglobin A1c level, the tight blood sugar control may prove to reduce risk. The results of the study should be out in the year 2010.
Robert M Cohen, MD
Professor of Clinical Medicine
College of Medicine
University of Cincinnati