Simplifying HbA1c for Diabetics

Most diabetic patients are quite familiar with blood glucose levels expressed as mg/dL (or mmol/L in some countries). They know what their fasting level should be (below 100 mg/dL is ideal), and that they should try to have their 2-hour post-meal level return to the low 100s. Their physicians, on the other hand, more commonly use the HbA1c (or percent glycated hemoglobin) as an indicator of control of their disease; the HbA1c really represents the average blood glucose level over the previous 4 weeks.

Harvard Medical School researchers have shown that they can simplify this situation by expressing the HbA1c value as the actual average glucose level (AG), a number that can be more readily understood by patients and one that could be used for better communication between doctor and patient. A study of over 500 subjects (both type 1 and type 2 diabetics as well as some non-diabetics) provided roughly 2,700 blood glucose levels from each subject. From the close correlation between the HbA1c and averaged glucose levels they derived a simple formula:

AG (mg/dL) = 28.7 x HbA1c – 46.7.

The researchers propose that average glucose levels be reported as mg/dL, mmol/L, and as %age HbA1c, until the AG in mg/dL is generally accepted. According to specialists who commented on this idea, it may take years for the concept to become generally accepted. However, in case you’re interested, here’s a small conversion table:

6.0% HbA1c = 125 mg/dL AG

6.5% hbA1c = 140 mg/dL AG

7.0% HbA1c = 154 mg/dL AG

7.5% HbA1c = 168.5 mg/dL AG

8.0% HbA1c = 183 mg/dL AG

8.5% HbA1c = 197 mg/dL AG

These average glucose values will have some meaning for you if you’ve been measuring your blood sugar for some time. You’ll be ready when your doctor tells you about the new units being used to monitor your likely progress over the last 3 months or so.