A1c — a Better Risk Indicator of Diabetes

For decades, the diagnosis of diabetes has been based on glucose fasting test.  American Diabetes Association (ADA) has not previously recommended the use of A1c for diagnosing diabetes, in part due to lack of standardization of the assay. However, A1c assays are now highly standardized, and their results can be uniformly applied both temporally and across populations[1].  In this article, we will examine why Reuters reported that A1c diabetes test is a better indicator of risk[2].

What's Hemoblogin A1c?

Hemoglobin A1c reading is a measure of the average blood sugar level over the preceding three months. Sugar sticks to protein, and when it's around for a long time, it gets harder and harder to remove.  The red blood cells that circulate in the body live for a hundred days before they die, and when sugar sticks to these cells, it give doctors an idea of how much sugar has been around for the preceding three months[3].

Advantages and Disadvantages of A1c


Compared to glucose fasting test, A1c test has the following advantages:[3]


and the following disadvantages:

Sample Test Report

Table 1.  If greater than 93.5 percent of your blood’s hemoglobin isn’t irreversibly bound to glucose—meaning it’s mostly the HbA1 type not HbA1c, you're good.

Estimated Average Glucose (eAG) is calculated using the equation[5]:

Note that the diagnostic test should be performed using a method certified by the National Glycohemoglobin Standardization Program (NGSP) and standardized or traceable to the Diabetes Control and Complications Trial (DCCT) reference assay.

References