A1C (HbA1c): Hemoglobin A1c
Hemoglobin A1c (HbA1c or A1C) measures the percentage of glycated hemoglobin in the blood, reflecting average blood glucose levels over the preceding 2–3 months and serving as the primary long-term diabetes management metric.
What is A1C?
Hemoglobin A1c (A1C) is formed when glucose in the bloodstream binds to hemoglobin in red blood cells. Since red blood cells live approximately 90–120 days, the proportion of glycated hemoglobin reflects average blood glucose over that period. An A1C of 7% corresponds to an estimated average glucose (eAG) of approximately 154 mg/dL; an A1C of 8% corresponds to ~183 mg/dL.
Clinical Target Ranges
The American Diabetes Association (ADA) provides the following glycaemic target guidance:
- <7%: Target for most non-pregnant adults with Type 1 or Type 2 diabetes without significant hypoglycaemia risk
- <8%: Appropriate for patients with limited life expectancy, advanced complications, extensive comorbidities, or history of severe hypoglycaemia
- <6.5%: May be targeted in select patients early in disease course without significant CVD risk or hypoglycaemia history
- Individualised targets: Required for elderly, paediatric, and pregnant patients
A1C as a MIPS Quality Measure
NQF measure 0059 (Diabetes: Hemoglobin A1c Poor Control > 9%) is one of the most commonly reported MIPS quality measures. This is an inverse measure — lower performance rates are better. The denominator is all patients 18–75 with Type 1 or Type 2 diabetes who had at least one qualifying visit during the performance period. The numerator is patients with an A1C > 9% or without an A1C result. NCQA's HEDIS also includes a Comprehensive Diabetes Care (CDC) measure set that tracks A1C < 8% at the health plan level.
A1C in Population Health Analytics
Tracking A1C at the population level reveals patients overdue for testing (any diabetic patient without an A1C in the past 12 months represents both a care gap and a quality measure denominator who should be excluded from poor control calculations) and patients with persistently poor control who may benefit from intensified management, CCM enrolment, or specialist referral. Real-time A1C dashboards stratified by provider, payer, and risk tier are foundational to any effective diabetes population health programme.