You may have heard of a diabetes test called a hemoglobin A1c, sometimes called HgbA1c, HbA1c, or just A1C. What is an A1C test, and what should you know about it?
HgbA1c is hemoglobin (pronounced HE-mo-glow-bin) that has sugar attached to it. Hemoglobin is the protein that carries oxygen from the lungs to all the cells of the body. Hemoglobin is an important component of red blood cells (RBCs).
Nearly all cells in the human body need oxygen to power them. All animals with backbones, except one family of fish, have hemoglobin. Hemoglobin and molecules like it are also found in many invertebrates, plants, and fungi.
Types of hemoglobin
The “A” in Hemoglobin A (HgbA) stands for “adult.” After a person reaches six months of age, nearly all the hemoglobin is type A.
About 98% of HgbA is type 1, or HgBA1. There is also HgBA2 (in addition to other types of hemoglobin), but not much. Type A1 has subtypes A1a, A1b, A1c, and others. Type A1c is the most common, making up about two-thirds of hemoglobin with glucose attached.
HgbA1c is a good marker for glucose control, because the more glucose is circulating in the blood, the more hemoglobin will be glycated (covered with sugar).
What an A1C test means
Once hemoglobin is glycated, it stays that way until the red blood cell dies. Red blood cells live an average of three to four months. That is why your A1C level indicates your average glucose over the last few months.
A1C results are expressed as the percentage of all hemoglobin that is glycated. An A1C of 7.0% means an average blood glucose level of 154 mg/dl, according to the American Diabetes Association (ADA). You can use this calculator to convert your A1C to an estimated average blood glucose number.
However, A1C tests can sometimes mislead because:
• Newer blood cells will be less glycated than older ones, because they haven’t had as much time to be exposed to glucose. So if you have a lot of new cells, for example after a blood loss, your A1C will be lower.
• Anemia will usually give you a higher A1C, perhaps because with less hemoglobin, a higher percentage of it will be exposed to glucose.
Low iron levels are a major cause of anemia. If you are anemic, iron supplements may potentially lower your A1C.
• In kidney disease, A1C may appear higher than it really is, because of anemia and other factors. But it can also read falsely low because blood cells aren’t lasting long enough to become glycated.
• According to an article in the Journal of Endocrinology & Metabolism, liver disease can give a falsely low A1C.
A1C test tips
You don’t need to fast or change medicine schedules for an A1C test.
Doctors usually order A1C tests every three months, six months, or year. There’s usually no good reason to do it more often.
You can test your own A1C. Kits cost about $40 for two tests at Walgreens, with a variety of prices and products available at other stores.
Interpreting A1C results
An A1C below 5.7% is considered normal. From 5.7% to 6.4% is classed as prediabetes. An A1C of 6.5% or higher gets you diagnosed with diabetes (the result should be confirmed with a test on a second day prior to diagnosis).
For a person with diabetes, many doctors recommend aiming for an A1C of 7.0% or below. That level will still put you at risk for long-term complications, though. Most experts believe the lower your A1C, the better, down to about 5%. Lowering it further doesn’t hurt (except for the risk of low blood glucose levels that comes with tight control), but it may not help.
ADA says A1C goals should be tailored to individual patients. Older people are often advised to relax their goals, accepting numbers up to 8.0% or even higher. You and your doctor will have to decide what’s right for you.
Your A1C level reflects two things: your fasting glucose level and your postprandial (after-meal) levels. If your A1C is higher than you want, you might want to talk with your diabetes educator or doctor to see which is happening for you and how to manage it.
Lowering your A1C
Since A1C reflects average glucose, any good care or self-management will tend to reduce it. Exercising, reducing starch and sugar intake, reducing stress, and getting on the right medicines are always good ideas.
Vitamin C in quantities of 1,000 milligrams a day or more was found in an Iranian study to reduce A1C. Other supplements could help, too. Plant medicines like bitter melon may definitely help a lot of people lower their A1C.
Fructosamine levels are good alternatives to A1C. Fructosamine measures the amount of glucose stuck to the protein albumin.
Fructosamine is not affected by blood cells dying off or being born, so it’s more accurate than A1C if you have anemia, blood loss, pregnancy, or other conditions affecting your blood. Fructosamine gives a measure of average glucose over the previous 2–3 weeks, not 12 weeks like A1C.
You might ask your doctor about a fructosamine test if A1C doesn’t work well for you for some reason. There are no home fructosamine tests.
Fun facts about hemoglobin
Crabs and some other invertebrates have blue blood, because their kind of hemoglobin has a copper atom at the center instead of iron. Plants have chlorophyll to do some of what hemoglobin does, and some other things. Plants are green because chlorophyll has a magnesium atom at the center. The molecules are otherwise quite similar.
The healthy adult human body makes about two million new red blood cells every second. That requires a lot of hemoglobin.