The big picture: HbA1c, or glycated hemoglobin, is a critical marker in understanding and managing diabetes and cardiovascular diseases. This measurement reflects the average blood glucose level over about 90 days.

Diabetes diagnosis: Diabetes, a disorder characterized by improper blood glucose regulation, manifests primarily in two forms. Type 1 diabetes results from an absence of insulin, while Type 2, more common, arises from insulin resistance. An HbA1c level exceeding 6.5% generally indicates diabetes, while levels between 5.7% and 6.4% signal a prediabetic state.

Downstream impact: Type 2 diabetes is intricately linked with lifestyle and genetic factors, such as obesity and family history. Beyond elevated blood sugar, diabetes escalates the risk of various heart disease factors, including increased LDL cholesterol, decreased HDL cholesterol, and increased triglycerides. Notably, people with diabetes face up to a fourfold increase in the risk of developing cardiovascular disease.

How it works: Glucose, the sugar in your blood, binds to hemoglobin in red blood cells. The lifespan of these cells (90-120 days) makes HbA1c a reliable indicator of average blood glucose over this time period. Higher blood sugar levels lead to more glucose binding to hemoglobin, thereby increasing the HbA1c value.

Yes, but: It's not a perfect system. HbA1c's accuracy depends on the assumption of a standard red blood cell lifespan of 90-120 days, which can vary among individuals. This variance can lead to misleading HbA1c readings, underestimating or overestimating average blood glucose levels.

For example, someone with smaller red blood cells that persist for a longer time, results in an overestimation of their average blood glucose based on HbA1c.
Conversely, someone with larger red blood cells, can lead to accelerated destruction and an HbA1c that underestimates their average blood glucose levels.
The use of continuous glucose monitoring (CGM) data can provide more accurate insights into average blood sugar levels compared to HbA1c in such cases.