Medically Reviewed By: Tom Iarocci, MD

People who have diabetes will often take the A1C test, and this same test is also sometimes used as a screening test, when a person is suspected of having diabetes or prediabetes. A1C is a blood test that measures what the levels of blood sugar, or blood glucose, have been on your body over a period of about two to three months. You may have an A1C performed twice a year if your diabetes has been stable and well-controlled; however, this test may be done more frequently, as often as four times a year, if you and your doctor are still trying to work things out in terms of your therapies and your blood sugar goals. A1C tends to be the most common name used for the test these days, but other names for the same test include Hba1c, the hemoglobin A1c, or the glycohemoglobin test.

Using A1C In The Diagnosis Of Prediabetes And Type 2 Diabetes:

The A1C test can be used in some instances as a standalone test to diagnose prediabetes and type 2 diabetes, but in other cases, further testing may be required to establish these diagnoses. It is possible for a single A1C test to be somewhat off, and there can be variability by ethnicity and other factors. Sometimes your doctor will ask for the test to be repeated, or there might be a preference given to a different glucose test in diagnosing your condition. As far as A1C results go, levels below 5.7% are considered normal; levels between 5.7% and 6.4% are indicative of prediabetes; and anything 6.5% or above is considered diabetes, with the caveat that any test used for the diagnosis of diabetes requires confirmation with a second measurement, unless there are clear symptoms of diabetes.

Statistically, unless you make certain lifestyle changes, having prediabetes means you are very likely to go on to develop type 2 diabetes in the next 10 years. If you have been diagnosed with prediabetes, you may be tested more regularly to see if you have improved your sugar levels. The progression from prediabetes to diabetes is one of the reasons why diet, exercise and intensive lifestyle changes are so important to start working on earlier, rather than later.

The Relation Between A1C And Average Glucose:

One of the problems that people may have with the A1C test is that the results are expressed as a percentage, whereas the at-home blood sugar measurements are given in milligrams per deciliter (mg/dl). To help people with diabetes get a better sense for what A1C readings really mean in terms of numbers they are used to seeing, conversion from A1C to eAG, or estimated average glucose, can be done. As such, an A1C of 6% equates to 125mg/dl, 7% to 154mg/dl, 8% to 183mg/dl, 9% to 212mg/dl, and so on. You can also find these calculators, or converters, on the web, on sites like this one from the American Diabetes Association.

A1C Targets:

Not all people with diabetes have the same goals or target A1C values. A person’s target is determined based on the overall health and diabetes history, and it is a determination that is is made together with the health care provider. Staying below 7% (154mg/dl) significantly reduces the chances many serious complications of diabetes. This protective benefit is weighed against potential risks associated with a person of trying to achieve that target, namely blood sugar going too low.

Going well below 7% to 6.5%, for instance, may be possible for some people, but can lead to low blood glucose, or hypoglycemia in others. A goal A1C result between 7% and 8% may be more appropriate when there are extenuating circumstances, such as a limited life expectancy, or really intractable diabetes in someone who has lived with the condition for years, glucose levels that just doesn’t respond to therapy enough to get the A1C down; or those who suffer from sever hypoglycemia, and those who already have advanced complications as a result of diabetes, including nerve damage, chronic kidney disease, or cardiovascular disease.