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When I was first diagnosed with diabetes, my nurse educator introduced me to the "diabetic truth detector," HbA1C. Glycosylated hemoglobin, or hemoglobin A1C, she insisted, would give my doctor the truth behind my blood sugar readings in a test it was impossible to fake.
Actually, it's impossible to fake the everyday blood glucose readings diabetics need to take first thing in the morning and after every meal, too, but HbA1C is a measure of long-term blood sugar control. What most doctors don't tell diabetics is that it is very easy to manipulate HbA1C through healthy habits.
What Is Glycosylated Hemoglobin?
Glycosylated (or glycated) hemoglobin is a small fraction of the body's oxygen-carrying hemoglobin protein that is chemically bound to glucose. During their 90-day life span, some red blood cells are exposed to enough sugar as they circulate in the bloodstream that a certain amount of glucose "sticks." The higher the average glucose level in the bloodstream, the higher the percentage of red blood cells that contain glycosylated hemoglobin. Everyone has at least a small percentage of HbA1C, although diabetics may have 7 percent, 10 percent, 20 percent, or even more. Acceptable diabetic control usually results in a 6 percent to 7.5 percent HbA1C range, while a HbA1C normal range (some doctors urge their diabetic patients to strive for 7 percent), for non-diabetics, is more on the lines of 4.5 to 5 percent.
While blood glucose levels go up and down constantly, even in healthy people, HbA1C levels are not affected by hour-to-hour changes in diabetic control. HbA1C percentages change over the entire life span of the red blood cell, which is the reason doctors test HbA1C about once every 90 days.
Understanding Surprises in HbA1C Readings
When diabetics get HbA1C readings that don't line up with the blood sugar readings they take at home, they usually are taking fasting blood sugar levels but skipping post-prandial (after-meal) readings. Especially in the early stages of type 2 diabetes, the insulin-making beta-cells of the pancreas may retain the ability to lower blood sugar concentrations back down to normal overnight. They may lack the ability to "unpack" stored insulin to normalize blood sugar levels quickly after meals. Taking a fasting blood sugar level every morning may give the impression that diabetes is under good control, when in fact high glucose levels for hours after meals are increasing the underlying problem, insulin resistance, and increasing the risk of complications.
Any time blood sugar levels exceed about 170 mg/dl (9.4 mmol/L), insulin resistance increases. Cells in the skeletal muscles and liver shut down receptors for insulin to protect themselves from receiving too much glucose. In the early stages of type 2 diabetes, the pancreas responds by pumping out more insulin, whereupon muscle and liver cells shut down still more insulin receptors to become even more insulin resistant. High levels of insulin in the bloodstream deactivate an enzyme essential for releasing fat from fat cells to be burned elsewhere in the body, so it becomes harder and harder to avoid weight gain. Glycated proteins on nerve cells can spur peripheral neuropathy, retinopathy, and even foot infections (as nerves to the sweat glands fail to keep the skin moist, and cracks in the skin admit infection). All of this can happen to people who think, on the basis of taking just one blood sugar reading every morning, that their diabetes is in good control.