If you're a newly diagnosed diabetic, or you live with the disease but are trying new approaches to getting your disease under control, the hemoglobin A1c tests may be some of the best tests available to your and your doctor. Unlike a single blood glucose test or home glucose monitoring, hemoglobin A1c (HbA1c) test results will provide you with better information about how you are managing your diabetes over extended periods of time.
Diabetes is a serious metabolic disease that results in the body not properly processing glucose in the blood. Carbohydrates in your diet are broken down in the small intestine and released into the bloodstream as glucose--one of the body's primary fuel supplies. Many organs like the brain and the nervous system cannot survive without a constant supply of glucose. When it dips too low, you feel lightheaded and irritable. When glucose levels remain too high, they can lead to kidney failure, heart disease, blindness and loss of limbs.
Two Types of Diabetes
There are two types of diabetes: type I, formerly called insulin-dependent diabetes, and type II, formerly called noninsulin-dependent diabetes. Type I diabetics fail to make enough insulin. Insulin is a hormone made in the pancreas and helps the tissues use glucose circulating in the blood. Type II diabetics make enough insulin, but their tissues are insensitive to insulin. For both types of diabetes, the results are the same; the body starves in the presence of plenty of fuel. The treatment for type I diabetes typically involves diet, exercise and the exogenous injection of insulin--up to several times a day. Type II diabetics frequently respond well through diet and exercise as well as oral medications; rarely is injected insulin necessary. There is also a very high correlation between body weight and type II diabetes. When the diabetic loses weight, their symptoms subside. But diabetics need to know if their treatment is working.
Blood Glucose Testing Methods
When diabetics are first suspected of having the disease, they exhibit typical symptoms--sudden loss of weight, frequent urination and profound appetite--all for no explained reasons. The first round of tests usually involves a fasting glucose test (FGT). After fasting for 12 hours, your blood is measured for blood glucose levels. The normal range is between 70 to 110 mg/dl. If your test comes back high, your doctor may order a glucose tolerance test (GTT). After drinking approximately 100 mg of glucose, your doctor monitors how quickly your blood glucose returns to normal--usually less than 140 mg/dl after 2 hours. If that test comes back abnormally high, you could be a diabetic. But there's one more test that will help you doctor to determine if you are just having periodically high glucose results or if you truly have long-term glucose problems: the hemoglobin A1c test.
Hemoglobin A1c Test
Red blood cells (RBC) circulate through your blood, bathed in a sea of plasma. Red blood cells perform a number of important functions for the body, including carrying oxygen to the tissues. The RBCs contain hemoglobin--the portion of the cells that carry oxygen to exercising muscles and other active tissues. By coincidence, glucose attaches--called glycating or glycosylating--to the same hemoglobin, so in essence, glucose competes with oxygen for the hemoglobin. Normally, that's not a problem if the glucose levels are low--5 percent or less. However, if glucose levels remain high--over 7 percent--the tissues cannot get the oxygen and nutrients that they need, and their health begins to suffer. The result is a long list of secondary complications associated with diabetes like kidney failure, nerve damage, blindness and even loss of vision. It's important that the HbA1c values are kept down. The link at the bottom of this page will help you to convert HbA1c scores into blood glucose equivalents.
The Importance of HbA1c
All of the previously described methods of testing blood glucose are important in their own right and give your physician important information about how well your diabetes is being managed. But they are also fraught with limitations. For instance, fasting glucose tests only provide information concerning your blood glucose at that particular point in time. One day it could be high; the next day it could be low. Glucose tolerance tests also provide valuable information, but again give specific information over a few hours. Even home blood glucose monitoring can only tell you how well you're doing at that point in the day.
Hemoglobin A1c, however, measures the average blood glucose levels over the entire lifespan of the red blood cell--approximately 120 days. So even if you're having an up or down day, the HbA1c test provides you with your average blood glucose levels over 3 months--a much more accurate indicator of diabetes management.
Which Test Is Better
The important thing to understand is that no one test is perfect; they all have their strengths and weaknesses. Fasting glucose and home glucose monitoring are great ways to monitor short-term treatment changes. They can provide information that HbA1c testing will not. On the other hand, once you feel that you have your diabetes under control, an HbA1c test will provide information that home monitoring tests can't, because it represents long-term program compliance. If your doctor feels that it's time to change your medications, diet, exercise or all three, he may choose to use a combination of all of the tests. They all have their own unique value.
- "The Relationship Between Glycosylated Hemoglobin and Plasma Lactate Accumulation During Submaximal Exercise in the Type II Diabetic"; Allen R. Smith; Thesis, San Diego State University, 1983
- DiabetesChart.org: HbA1c Test Results and Their Plasma Blood Glucose Equivalents