What are the reference ranges for Hemoglobin A1c (HbA1c)?

From the Guidelines

HbA1c reference ranges typically vary between 4% to 6% for people without diabetes, while for diabetic patients, treatment targets are generally below 7% for most adults, though this may be individualized based on patient factors, as suggested by the American Diabetes Association 1. The American Diabetes Association recommends that in general, an HbA1c target <7% (53 mmol/mol) is desirable for many nonpregnant adults, with higher values recommended for children and adolescents, balancing the acute risks of hypoglycemia against the long-term benefits on complications 1.

• For older adults or those with comorbidities, less stringent targets of 7.5-8.5% may be appropriate, as they are less likely to benefit from intensive glucose control and more likely to have risks from treatment 1.
• For pregnant women, tighter control with targets below 6-6.5% is recommended to reduce complications, as stringent control of HbA1c values during pregnancy decreases congenital malformations, large-for-date infants, and the complications of pregnancy and delivery that can otherwise occur when glycemic control is not carefully managed 1.
• HbA1c reflects average blood glucose levels over approximately 2-3 months, as it measures the percentage of hemoglobin molecules with glucose attached, providing a more stable assessment of glycemic control than point-in-time glucose measurements.
• Certain conditions like anemia, hemoglobinopathies, recent blood transfusions, or kidney disease can affect HbA1c results, potentially requiring alternative methods to assess glycemic control in these situations.
• The clinical implications of the small, but statistically significant, progressive increase of normal HbA1c levels with aging remains to be determined, and the effects of race on HbA1c values remain controversial, with some studies suggesting a relatively higher HbA1c in Black and Hispanic populations than in White populations at the same level of glycemia 1. The most recent guideline from the American College of Physicians suggests aiming to achieve HbA1C levels between 7% and 8% in most adults with type 2 diabetes and deintensifying pharmacologic treatments in adults with HbA1C levels less than 6.5%, with an individualized glycemic goal based on risk for hypoglycemia, life expectancy, diabetes duration, established vascular complications, major comorbidities, patient preferences and access to resources, capacity for adequate monitoring of hypoglycemia, and other harms 1.

From the Research

Reference Ranges for Hemoglobin A1c (HbA1c)

The reference ranges for Hemoglobin A1c (HbA1c) are as follows:

• The target HbA1c should be 7% or lower, as stated in the study 2
• Current guidelines specify HbA1c targets around or less than 7.0%, with more (<6.5%) or less (<8%) stringent goals being appropriate for selected patients, according to the study 3
• The American Diabetes Association recommends different A1C targets in older adults based on comorbid health status, with a target of <7% being reasonable for some older adults with diabetes, as indicated in the study 4
• A study on GLP-1 receptor agonists found that a significant proportion of patients with type 2 diabetes can achieve the HbA1c goal <7% with these medications, with baseline HbA1c being the best predictor for achievement of A1c target, as reported in the study 5

Key Considerations

• The treatment of diabetes mellitus is focused on the prevention of micro- and macrovascular complications, and the target HbA1c should be set accordingly, as discussed in the study 2
• HbA1c should not be interpreted in isolation, and measurement accuracy and other parameters, including treatment goals and comorbidities, need to be considered, as stated in the study 6
• The attainment of the HbA1c target ultimately depends on the target set by the physician, and both "a priori" and "a posteriori" approaches may be useful for making therapeutic decisions, according to the study 3