Hemoglobin A1C Blood Test Isn't Perfect

The hemoglobin A1C is a great blood test for type 2 diabetics, but not for diagnosing diabetes.

Don't misunderstand. I love the hemoglobin A1C blood test. It doesn't require fasting. It can be done in the doctor's office with a fingerstick just like your glucose monitor, and you can know the results before you leave the office. And it lets you know how your blood sugar has been doing over the past two or three months. It sounds perfect.

But it isn't. For diabetes management you and I need to know what our blood sugar is doing all the time, not just every three months. A great HGA1C reading does not mean there have been no hyperglycemic or hypoglycemic episodes over that time. So the hemoglobin A1C cannot replace daily checks with a glucose monitor and log book records.

Taken together with daily readings, the hemoglobin A1C gives an accurate picture of whether you are keeping your blood sugar in the ranges that will keep away the complications. There is more and more evidence that an HGA1C between 6.5 and 7 will do just that.

And here's an encouraging fact. If your A1C was 9 and you lower it to 8, there is a 20% reduction in risk of complications even though you aren't in the target range yet. That's good to know. You should also know that the American Diabetic Association says to get the test done every three months if your are diabetic.

Here's how it works. Hemoglobin is the medical term for red blood cells, and glycated hemoglobin is the term for red blood cells with sugar stuck to them. Over the life of a red blood cell, which is 120 days if all goes well, more and more sugar sticks to it as it travels through your bloodstream.

The amount can be measured accurately, and doctors know how much should be on each normal cell. If the level is high, that signals diabetes. The amount is reported as a percentage. That is why HGA1C numbers are so different from the readings you get from your glucose monitor.

So What's a Good Number?

This is where things get a little muddy. Depending on where you go for numbers, you'll 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 agreed that 6.5% is a better goal.

Non-diabetics have numbers in the range of 4-5.9%, and when the test number goes over 6.0%, some doctors tell their patients they might be diabetic. This is the danger of using the HGA1C to diagnose diabetes. Here are some reasons why.

There can be at least a half percentage point difference between two tests depending on how they are done. With home testing (a kit you can buy), the blood from a fingerstick is put on a card and mailed away to be tested.

The doctor's office test is done with a machine that gives results in 6 minutes but can be off a little because of the method. The most accurate test is done with a vial of blood at a testing facility or hospital, because they have national standards for constant recalibration, and the test is read using a more sophisticated method.

But even after an accurate test, the numbers can be read in different ways. 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 says it is 135. At 7% it might be 154 or 170. Which one is "right?"

Small discrepancies are not a problem if you know you are diabetic and are just evaluating how tight your blood sugar control is long term. But when 5.9% is normal and 6% means prediabetic according to what your doctor tells you, that tenth of a percent matters a lot for your peace of mind.

And there are other problems too. Anything that affects the life or health of red blood cells can make the hemoglobin A1C tests inaccurate for diagnosing diabetes. Any kind of anemia or illness, a change in medication, and even donating blood can affect the test. It is not used for testing gestational diabetes because of its limitations, and doctors still use the glucose tolerance test for that.

For diagnosing diabetes, the glucose tolerance test is still the best choice. Endocrinologists agree on this. So why does a family doctor use the hemoglobin A1C for diagnosing? Perhaps because he or she is not usually a diabetes specialist, and if the HGA1C is sold as the newest way to diagnose diabetes, it's going to be hard to resist.

Diabetes is probably in half of the patients over 40 in a doctor's practice, and the machine is cutting edge stuff. But the glucose tolerance test is still the best way to know if you are prediabetic, diabetic or just fine.

It takes a while but it is an accurate picture of how your body reacts to glucose. You don't have to worry. It isn't painful (unless you count fasting and a few fingersticks). So if you know someone who has been diagnosed by a hemoglobin A1C test, I hope you advise them to get the GTT test for a confirmation and to look for an endocrinologist.

I do love the A1C test, being a type 2 diabetic, because when I'm below 7 I know I'm doing well, and I have seen proof of that good blood sugar control in my own peripheral neuropathy symptoms. When the test is used for that purpose, it's fine. I love it when my doctor says, "Do you know your hemoglobin A1C?" and I say, "Yep, it's 6.8," and the doctor says, "Wow, that's great!"

Those are words I don't hear from my doctor often enough.

Martha Zimmer invites you to visit her website and learn more about type 2 diabetes, its complications and how you can deal with them, as well as great tips for eating healthy that will make living with diabetes less painful.

Go to http://www.a-diabetic-life.com and find out what you can do to avoid many of the pitfalls of this life-changing condition, like paying for cures that don't work and spending money for things you could have gotten free. Martha has made the mistakes and done the research so you don't have to.

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