A clinical blood test used to measure the average blood sugar levels of an individual over the preceding two to three months. It specifically measures the percentage of hemoglobin—the oxygen-carrying protein in red blood cells—that has glucose attached to it, a process known as glycation. Because red blood cells have a lifespan of approximately 120 days, the A1C provides a reliable long-term view of glycemic control that daily finger-prick tests cannot offer.
In the context of metabolic health, an A1C level below 5.7% is considered normal, while levels between 5.7% and 6.4% indicate prediabetes. A level of 6.5% or higher on two separate tests indicates type 2 diabetes. Lowering A1C through dietary interventions, such as reducing refined carbohydrate intake, is a primary goal in reversing metabolic syndrome and reducing the risk of long-term microvascular and macrovascular complications.
The definitive guide by Russell Clark, FNP-C, APRN