In Continuous Glucose Monitoring (CGM), eHbA1C stands for estimated HbA1C, and it differs from the actual lab-measured HbA1C in several ways:

Comparison Table

Item HbA1C (Lab Test) eHbA1C (Estimated)
Source Measured through a blood test in a lab Calculated by the CGM system from glucose data
Time Span Reflects average blood glucose over 2–3 months Based on recent days or weeks of CGM data
Accuracy Clinical standard, widely accepted Approximate value, affected by device and algorithm
Name HbA1C (Glycohemoglobin A1C) eHbA1C (Estimated A1C), also known as GMI

Key Notes

  • eHbA1C is an estimate, useful for tracking glucose trends, but it should not replace lab-tested HbA1C.
  • Some CGM systems refer to eHbA1C as GMI (Glucose Management Indicator), which serves a similar purpose.

Summary

eHbA1C provides an estimated A1C value based on CGM data. While helpful for ongoing glucose management, it is not as precise as laboratory HbA1C tests. Both can be used together to better understand and manage blood glucose control.