Diabetics used to depend only on urine tests or daily finger sticks to measure their blood sugars. These tests were accurate, but only in the moment. As an overall measurement of blood sugar control, they were very limited, as blood sugar can vary wildly depending on the time of day, activity levels, even hormone changes. Some people may have high blood sugars at 3 a.m. and be totally unaware of it.
Once A1C tests became available in the 1980s, they became an important tool in controlling diabetes. A1C tests measure average blood glucose over the past two to three months. So even if you have a high fasting blood sugar, your overall blood sugars may be normal, or vice versa. A normal fasting blood sugar may not eliminate the possibility of type 2 diabetes. This is why A1C tests are now being used for diagnosis and screening of prediabetes. Because they don’t require fasting, the test can be given as part of an overall blood screening.
What exactly does A1C measure?
A1C measures the amount of glucose in hemoglobin in the blood. Hemoglobin is a protein found inside red blood cells that carry oxygen to the body. Hemoglobin cells are constantly dying and regenerating, but they have a lifespan of approximately three months. Glucose attaches (glycates) to hemoglobin, so the record of how much glucose is attached to your hemoglobin also lasts for about three months. If there is too much glucose attached to the hemoglobin cells, you will have a high A1C. If the amount of glucose is normal, your A1C will be normal.
The reason that the test is effective is the lifespan of the hemoglobin cells. Let’s say your blood glucose was high last week or last month, but is normal now. Your hemoglobin will carry a “record” of last week’s high blood glucose in the form of more A1C in your blood. The glucose that was attached to the hemoglobin during the past three months will still be recorded by the test, as the cells live approximately three months. The A1C test provides an average of your blood sugar readings for the past three months. It’s not accurate for any given day, but it gives the doctor a good idea of how effective your blood sugar control has been over time.
What do the numbers mean?
Someone who is not diabetic will have about five percent of their hemoglobin glycated. This means that if your A1C is below 5.7, you don’t have to worry. A normal A1C level is below 5.7 percent; 6.5 percent or above indicates diabetes; 5.7 to 6.4 percent is prediabetes. To monitor your overall glucose control, diabetics should have an A1C at least twice a year.
Anyone who has had diabetes for any length of time knows that A1C tests haven’t been reliable until recently. In the past, many different types of A1C tests gave different results depending on the lab that analyzed them. However, accuracy has been improved by the National Glycohemoglobin Standardization Program. Manufacturers of A1C tests now have to prove that their tests are consistent with those used in a major diabetes study. Even more recently, accurate home test kits have become available for purchase.
Accuracy is relative, however, when it comes to A1C or even blood glucose tests. The A1C test result can be up to half a percent higher or lower than the actual percentage. That means if your A1C is 6, it might indicate a range from 5.5 to 6.5. Some people may have a blood glucose test that indicates diabetes, while their A1C is normal, or vice versa. Before making a diagnosis of diabetes, your doctor should repeat the tests.
Some people may even get false results if they’re severely anemic, are in kidney failure, or have liver disease. Ethnic origin can also influence the test. People of African, Mediterranean, or Southeast Asian descent may have a less common type of hemoglobin that can interfere with some A1C tests.
What to do if your A1C number is high
If you’re in the early stages of the disease, small changes in lifestyle can make a big difference and even reverse diabetic results. Losing a few pounds or starting an exercise program can move you into the non-diabetic camp.
For those who have had prediabetes or diabetes for a long time, A1C results that are moving upward is a sign that you need to start on medication or change what you are already taking. You may also need to make other lifestyle changes and monitor your daily blood glucose more closely.