From the Guidelines
HbA1c is measured in two main units: percentage (%) and mmol/mol, with equivalent values including 5.7% = 39 mmol/mol, 6.5% = 48 mmol/mol, and 7.0% = 53 mmol/mol, which are used to diagnose diabetes and assess glycemic control 1.
Units of Measurement
The percentage scale typically ranges from 4% to 14%, while the mmol/mol scale ranges from about 20 to 130.
- To convert between these units, you can use the formula: mmol/mol = (% × 10.93) - 23.5, or conversely, % = (mmol/mol + 23.5) ÷ 10.93.
- These measurements reflect the same biological parameter - the percentage of hemoglobin with glucose attached - but are simply expressed in different numerical scales.
Clinical Significance
Healthcare providers use these values to diagnose diabetes, assess glycemic control over the previous 2-3 months, and adjust treatment plans accordingly 1.
- When reviewing your HbA1c results, it's essential to know which unit system your healthcare provider uses to properly interpret your glycemic control.
- The HbA1c goal for most nonpregnant adults is less than 7% 1, which has been shown to reduce microvascular complications of diabetes and mortality in those with type 1 diabetes.
Key Equivalent Values
Some common equivalent values include:
- 5.7% = 39 mmol/mol (prediabetes threshold)
- 6.5% = 48 mmol/mol (diabetes diagnosis threshold)
- 7.0% = 53 mmol/mol (common treatment target) These values are crucial in diagnosing and managing diabetes, and understanding the equivalent values in both units is essential for effective patient care 1.
From the Research
Units of Measurement for Hemoglobin A1c (HbA1c)
The units of measurement for HbA1c include:
- Percentage (%) 2, 3, 4
- Milligrams per deciliter (mg/dL) or millimoles per liter (mmol/L) 2
- Millimoles per mole (mmol/mol) 2, 3, 5, 6, 4
Equivalent Values
The equivalent values for HbA1c are:
- 6.5% is equivalent to 48 mmol/mol 3
- 5.7-6.4% is equivalent to 39-46 mmol/mol 3
- 6.0-6.4% is equivalent to 42-46 mmol/mol 3
- 50 mmol/mol is considered diagnostic of diabetes 6
- 40 mmol/mol represents normal glucose tolerance 6
- 41-49 mmol/mol requires cardiovascular risk assessment and lifestyle interventions with repeat HbA1c screening in 6-12 months 6