A is for A1C
A1C is the single most important number in diabetes care. It tells you what your blood sugar has been doing for the last three months — not just today, not just this morning, but on average.
A1C is a percentage. Higher means more sugar has been sticking to your red blood cells over time.
A1C measures the percentage of your hemoglobin that has glucose attached to it. Because red blood cells live about three months, A1C reflects your average blood sugar over that window. It's harder to game than a fasting glucose test, which only shows one moment in time.
The categories are straightforward. Under 5.7% is considered normal. 5.7%–6.4% is prediabetes. 6.5% or higher, on two separate tests, is diabetes. These cutoffs are the same regardless of age or ethnicity, even though the underlying risk varies.
For people with diabetes, the typical target is under 7%, though some doctors aim lower for younger patients and higher for older patients with other health concerns. Targets are personal — your doctor will set yours based on your situation.
What this means for you
If you have diabetes or prediabetes, A1C is the number you and your doctor will return to every three months. Knowing what yours is and where it's trending is the foundation of everything else.
What's your most recent A1C, if you know it? What was it before that?