The hemoglobin A1C is a great blood test for a diabetic. You can know how well your blood sugar control has been over a few months. But this test will not replace daily glucose monitors. It has other limitations too.
Still, the HbA1C blood test is my favorite of all type 2 diabetic tests. For one thing, it does not require fasting.
For another, it can be done in the doctor's office with a single fingerstick just like a glucose monitor test.
You get results in six minutes. Best of all, it lets you know how your blood sugar has been doing over the past two or three months.
The test sounds perfect, but it is not. For diabetes management you need to know what your blood sugar levels are every day.
Daily blood testing is still necessary, because a type 2 diabetic on insulin needs to know his glucose levels several times a day, not just every three months.
A great HBA1C reading does not mean there have been no hyperglycemic (high blood sugar) or hypoglycemic (low blood sugar) episodes over the last few months.
So the hemoglobin A1C cannot replace daily checks with your glucose monitor and good log book records. Your doctor always asks what your last daily reading was, and he likes to see your log book too.
Daily readings along with the A1C give a complete picture of what is going on with your diabetes treatment.
Taken together with daily readings, the hemoglobin A1C tells you if your blood sugar is staying in the range that will keep away the complications.
There is more and more evidence that an A1C between 6.5 and 7 will do just that. And here's an encouraging fact.
If your A1C was 9 and you lowered it to 8, there is a 20% reduction in your risk of complications.
That means you do not have to be in the best range yet to see benefits from better blood sugar control.
Hemoglobin is the medical term for red blood cells, and glycated hemoglobin is red blood cells with sugar "stuck" to them.
Over the life of a red blood cell, which is about 120 days if all goes well, more and more sugar gets stuck on it as it travels through your bloodstream.
The amount can be measured accurately, and researchers know about how much is on a normal red blood cell. If the number is too high, that signals diabetes.
The amount of sugar on red blood cells is reported as a percentage, which is why hemoglobin A1C numbers look so different from the readings you get on your glucose monitor.
This is where things get confusing. Depending on where you go, you will get slightly different answers. The American Diabetes Association says a number under 7%, or 7, is a good target for a diabetic.
Endocrinologists (M.D.'s who are diabetes specialists) have decided that 6.5% or lower is a better goal. But most doctors will be very pleased if your number is 7 or below. It means your blood sugar is staying under 150 over the long term.
The number would be much too high for someone without diabetes. But for a diabetic it means fewer complications, which is what we are aiming for.
Non-diabetics have hemoglobin A1C numbers in the range of 4-5.9%, so when the test number tests over 6.0%, some doctors tell their patients they are borderline diabetic.
But there can be at least a half percentage point (0.5%) difference between two tests depending on how they are done. This is the problem when using the hemoglobin A1C to diagnose diabetes.
With home testing (you can buy the kit at your pharmacy), the blood from a fingerstick used to be put on a card and mailed away.
The doctor's office test is done with a machine that gives results in 6 minutes. But this can be less accurate because of the method used to process the blood.
The most accurate test is done at a testing lab or hospital,
because they use national standards, constant recalibration, and a better method for processing blood.
But even after an accurate test, the results must be interpreted.
For example, one expert says that a 6% reading means
your blood sugar average for the past two or three months is 126, but
another one says your average was 135. At 7% it might be 154 or 170.
So which one is right?
Small discrepancies like those are not a problem if you are a diabetic who is using the test to see how tight your blood sugar control has been.
But when 5.9% is normal and 6% means you are prediabetic, a tenth of a percent means the difference
between normal and borderline diabetic. If the discrepancy could be five
times as much, this matters a lot to you.
Another problem is with the cells themselves. Whatever affects the life or health of red blood cells can give the hemoglobin A1C test a false result.
So using it to diagnose type 2 diabetes will not work if you have a problem with your blood, like anemia for example.
Any kind of illness, any change in medication, or just donating blood can affect the test, making it inaccurate.
This is why testing for gestational diabetes is not done with the hemoglobin A1C. Doctors still use the glucose tolerance test.
All blood tests have limitations, and this includes the A1C.
The hemoglobin A1C is fast, it is new, and it can be done right in a doctor's office. Diabetes is probably in half of the patients over 40 who pass through their offices, and anything that makes their job easier is appealing.
The glucose tolerance test, which was one of the first tests developed to smoke out diabetes, is still the gold standard for determining whether you are prediabetic or diabetic.
It takes two to four hours in a doctor's office, but it gives an accurate picture of how your body reacts to glucose. It is not painful, though, unless you count fasting and some fingersticks.
Okay, the glucose tolerance test is the best tool for finding prediabetes and type 2 diabetes. But as a type 2 diabetic, I love the A1C test.
Why? When the number is below 7, I know it means consistent blood sugar control over the past two or three months.
The benefits show in less numbness and tingling from diabetic neuropathy. It is also nice to have the A1C number before I leave the doctor's office.
Plus, when your doctor asks your A1C level, there is nothing like being able to say "6.9" or "6.5."
Then you hear him say, "Good for you!" When you are a type 2 diabetic you cannot hear that often enough.
[Go back to the top]Return to diabetes management from the hemoglobin A1C.