Estimated average glucose values translate hemoglobin A1C results into mg/dL or mmol/L, the same units used to report blood glucose levels. Therefore, eAG represents average daily glucose over the past 2-3 months. Expressing HbA1C as eAG appears to be appropriate for type 1 and type 2 diabetes (Nathan 2008).
Standard Range: 82-154 mg/dL (4.55-8.55 mmol/L)
The ODX Range: 85 -105 mg/dL (4.72-5.83 mmol/L)
Low eAG suggests the possibility of chronic hypoglycemia, including that caused by medications.
High eAG indicates chronically elevated blood glucose over the preceding 2-3 months. Elevated levels also suggest higher fasting glucose (Bozkaya 2010).
Estimated average glucose can be used to help evaluate blood glucose control over time. Since it is based on HbA1C results, it reflects average daily glucose over the past 3 months. It is expressed in the same units as glucose and therefore may be easier for patients to understand than HbA1C, which is expressed as a percentage.
Estimated average glucose reflects variability in levels whereas fasting glucose is a single “snapshot” of glucose control. Fasting glucose and eAG are not interchangeable even though they trend in the same direction. In one study of 2,315 type 2 diabetics, there was a significant difference between eAG and fasting glucose with median values of 171.2 mg/dL (9.5 mmol/L) and 135.2 mg/dL (7.5 mmol/L) respectively (Alzahrani 2020).
Research also suggests that the association between eAG and fasting glucose becomes stronger as glucose control worsens. A review of data from 4,673 type 2 diabetics found that those with the best glucose control had a mean eAG of 156.5 mg/dL (8.69 mmol/L) and a fasting plasma glucose (FPG) of 106.3 mg/dL (5.9 mmol/L). Those with average glucose control had a mean eAG of 181.9 mg/dL (10.1 mmol/L) and FPG of 148.823 mg/dL (8.26 mmol/L), while those with the worse glucose control had a mean eAG of 233.8 mg/dL (12.98 mmol/L) and a FPG of 234.1 mg/dL (12.99 mmol/L) (Ram 2021).
In one study of 3,891 diabetic patients, those with the lowest mean eAG at 125.1 mg/dL (6.94 mmol/L) had the lowest fasting glucose at 103.2 mg/dL (5.73 mmol/L) and lowest HbA1C at 6%. Those with the highest eAG at 229.6 mg/dL (12.74 mmol/L) had the highest fasting glucose at 281.7 mg/dL (15.63 mmol/L) and a HbA1C of 9.6% (Bozkaya 2010).
A review of the NHANES data of 13,792 individuals revealed that those without diabetes maintained estimated average glucose of 103 mg/dL (5.7 mmol/L); those with undiagnosed prediabetes had an eAG of 123 mg/dL (6.8 mmol/L), and those with undiagnosed diabetes had an eAG of 171 mg/dL (9.5 mmol/L) (Bowen 2015).
The American Diabetes Association provides a convenient calculator to convert HbA1C to eAGs (ADA eAG).
Alzahrani, Nabeel et al. “Can Fasting Blood Sugar be Used as an Indicator of Long-Term Diabetic Control Instead of Estimated Average Glucose?.” Clinical laboratory vol. 66,12 (2020): 10.7754/Clin.Lab.2020.200324. doi:10.7754/Clin.Lab.2020.200324
American Diabetes Association Estimated Average Glucose/A1C conversion calculator. https://professional.diabetes.org/diapro/glucose_calc
Bozkaya, Giray et al. “The association between estimated average glucose levels and fasting plasma glucose levels.” Clinics (Sao Paulo, Brazil) vol. 65,11 (2010): 1077-80. doi:10.1590/s1807-59322010001100003
Bowen, Michael E et al. “Random blood glucose: a robust risk factor for type 2 diabetes.” The Journal of clinical endocrinology and metabolism vol. 100,4 (2015): 1503-10. doi:10.1210/jc.2014-4116
Nathan, David M et al. “Translating the A1C assay into estimated average glucose values.” Diabetes care vol. 31,8 (2008): 1473-8. doi:10.2337/dc08-0545
Ram, Nanik et al. “Relationship Between Estimated Average Glucose (eAG) and Fasting Plasma Glucose in a Cohort of Pakistani Diabetic Subjects.” Cureus vol. 13,10 e18435. 2 Oct. 2021, doi:10.7759/cureus.18435