Beyond Blood Sugar: Testing A1c
November 1, 2012
What's your A1c? If you have diabetes and you don't know the answer, you should.
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Sometimes, living with diabetes can seem like a full-time job -- trying to keep up with everything you need to do for proper diabetes care. "Diabetes is a very time-consuming disease to manage well," says Karmeen Kulkarni, MS, RD, CDE, and former president of health care and education for the American Diabetes Association. "The medication, the food, the physical activity -- you add life in general to that whole picture and it ends up being quite challenging."
"The A1c [or glycated hemoglobin or HbA1c] is critical in the management of both type 1 and type 2 diabetes," says Fran Kaufman, MD, president of the American Diabetes Association. "It's a wonderful test."
Kaufman, who is also division head of endocrinology at the Children's Hospital Los Angeles, is not alone in her glowing assessment of the A1c. "The A1c test has been a revolutionary change in diabetes management," says David E. Goldstein, MD, chair of the NGSP steering committee, the organization that developed standards for A1c testing.
Despite enthusiastic reception by experts, the benefits of A1c testing are still not apparent to everyone. Not enough people with diabetes have their A1c tested regularly and, even when they do, many don't understand the results. In a survey conducted by the American Association of Diabetes Educators, only 24% of people with diabetes knew their A1c levels. Given the severe and life-threatening risks of diabetes -- such as heart disease and stroke -- that number is disturbingly low.
Everyone with diabetes is familiar with the standard, fasting blood-glucose test that is used to indicate your current blood sugar levels. The fasting test is the warhorse of diabetes management, and it helps you and your doctor see how your treatment is going.
But while the fasting test remains an important part of diabetes treatment, its weakness is that it is an indication of your glucose level only at the moment you take the test. A fasting blood sugar doesn't tell you anything about your blood-sugar levels the rest of the time.
The hemoglobin A1c test -- usually called the A1c -- fills this gap by testing your blood sugar in a different way. As your body processes blood sugar, small amounts of glucose naturally bond with hemoglobin, a protein in the red blood cells. What's significant is that the amount of glucose that combines with the hemoglobin is directly proportional to the total amount of glucose that is currently in your system.
As a result, the hemoglobin bonded with glucose (glycated hemoglobin, or A1c) can be used as an overall record of glucose levels for as long as the individual red blood cell lives, which is about two to three months. While a fasting test gives you an indication only of current glucose levels, the A1c gives you the big picture of what your average levels are over this whole two to three month period.
Goldstein says that fasting-glucose tests alone were not a very good indicator of how well a person was doing in controlling his or her blood sugars. He says that he and other experts used to be surprised by patients who appeared to have good glycemic control -- based on fasting sugars -- but who would then suddenly develop serious complications.
"By checking the A1c, we don't see surprises like that anymore," Goldstein tells WebMD. "When we monitor people in the long term, we don't see people with great A1c levels developing classic complications of diabetes."
The test itself is simple and quick and thanks to the work of the NGSP (formerly the National Glycohemoglobin Standardization Program), more than 90% of all A1c tests are now standardized, meaning that the results from different labs should be comparable. Experts are not yet sure how often people with diabetes need to have their A1c tested, but the American Diabetes Association settled on a range of two to four times per year based on current evidence.
How Low Should it Be?
But exactly where you should be on that scale is debated and the recommendations for target A1c levels vary. For instance, the American Diabetes Association recently changed its recommended A1c from under 8% to 7% or below. Meanwhile, the American Association of Clinical Endocrinologists (AACE) recommends an even lower number of less than 6.5%.
All of these different numbers might leave you a bit confused. However, the general rule is that the closer to a normal A1c a person can get, the better, provided that the glucose control is not so strict -- or tight, in medical terminology -- that it induces hypoglycemia, a level of blood sugar that is too low. Treatment almost always includes behavioral techniques, such as weight loss and exercise, and may include medications to lower blood sugar levels.
But it's important to know that not everyone can reach these goals. "I've been delighted with the number of patients I have with A1c levels in the low 6% area," says Paul Jellinger, MD, past president of the American Association of Endocrinologists. "But in some patients who have unstable blood sugar levels, you're content with 7.2% or 7.4%, since that's the best you can do."
Goldstein is somewhat doubtful of the new, lower targets. "I agree that people should strive for the lowest A1c possible," he says, "but most patients can't achieve either the ADA or the AACE goals with current therapies because they're so low. And I think that you have to be careful not to set a goal that most people can't attain."
So what's the upshot? Get your A1c tested regularly and consult with your doctor about what target you should set. In general, aim for below 6.5% or 7%, but understand that it may not always be possible to get there.
Doing it Yourself
At least one at-home test kit for A1c levels has been developed, and more are probably on the way. While it may be somewhat more convenient than trudging into the doctor's office, Goldstein and Kaufman are a little skeptical of their usefulness.
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