HbA1c

HbA1c (hemoglobin A1c) is a blood test that measures the average level of blood sugar (glucose) over the previous 2-3 months. It works by measuring the percentage of hemoglobin — the protein in red blood cells that carries oxygen — that has glucose attached to it (glycated hemoglobin). The higher your blood sugar has been over the past few months, the more glucose will be attached to your hemoglobin, and the higher your HbA1c result will be.

Because red blood cells have a lifespan of approximately 120 days, the HbA1c test reflects your average blood sugar over that entire period — not just a single moment in time, as a fasting glucose test does. This makes it a more comprehensive and reliable indicator of overall blood sugar control and is why it's the primary test used to diagnose diabetes, monitor diabetes management, and assess prediabetes risk.

HbA1c results are reported as a percentage. A normal HbA1c is below 5.7%. A result between 5.7% and 6.4% indicates prediabetes. A result of 6.5% or higher on two separate tests confirms a diabetes diagnosis. For people already diagnosed with diabetes, the target HbA1c is typically below 7%, though individualized targets may vary based on age, health status, and other factors.

If you've been diagnosed with or are at risk for type 2 diabetes, your HbA1c is one of the most important numbers in your health profile. Unlike a fasting glucose test that captures a single moment, HbA1c shows the bigger picture of your blood sugar control over months. This makes it invaluable for assessing whether your diabetes management plan — diet, exercise, medications — is working effectively.

For people with prediabetes, tracking HbA1c over time provides objective evidence of whether lifestyle changes are successfully preventing progression to diabetes. Even small reductions in HbA1c translate to meaningful reductions in the risk of diabetes-related complications including nerve damage, kidney disease, eye problems, and cardiovascular disease.