Understanding A1C and Estimated Average Glucose (eAG)
Last reviewed: September 6, 2026
A1C is a blood test that reflects your average glucose level during approximately the previous two to three months. It measures the percentage of hemoglobin in red blood cells that has glucose attached to it.
For many nonpregnant adults with diabetes, a common A1C goal is below 7%. Your personal goal may be higher or lower depending on your age, overall health, risk of low glucose, pregnancy, and other medical conditions.
Why A1C Matters
Keeping A1C within a good range can reduce the risk of diabetes-related eye, kidney, and nerve complications.
A1C is useful for following long-term glucose control, but it does not show daily highs, lows, or rapid changes. Two people can have the same A1C while experiencing very different glucose patterns.
What Is eAG?
Estimated average glucose, or eAG, translates A1C into the same mg/dL units shown by glucose meters and continuous glucose monitors.
Approximate comparisons are:
• A1C 6% = eAG 126 mg/dL
• A1C 7% = eAG 154 mg/dL
• A1C 8% = eAG 183 mg/dL
• A1C 9% = eAG 212 mg/dL
• A1C 10% = eAG 240 mg/dL
• A1C 11% = eAG 269 mg/dL
• A1C 12% = eAG 298 mg/dL
The eAG is calculated from A1C. It is an estimate and may not equal the average displayed by your glucose meter or CGM.
When A1C May Be Misleading
A1C depends partly on the lifespan and characteristics of red blood cells. It may be less reliable in people with:
• Anemia
• Recent blood loss or blood transfusion
• Advanced kidney disease
• Pregnancy
• Certain hemoglobin variants
• Conditions that shorten or lengthen red blood cell survival
A recent major improvement or worsening in glucose may also cause A1C to differ from current meter or CGM readings.
Looking Beyond A1C
A1C and eAG provide useful summaries, but neither shows when glucose is high or low. Meter readings, continuous glucose monitoring, Time in Range, and sometimes other laboratory tests can provide additional information.
If your A1C does not agree with your glucose readings, discuss the difference with your healthcare professional rather than assuming that either result is wrong.
Sources
American Diabetes Association. Standards of Care in Diabetes—2026.
American Diabetes Association. Understanding A1C.
National Institute of Diabetes and Digestive and Kidney Diseases. The A1C Test and Diabetes.
This information is provided for general education and does not replace individualized medical advice. Contact your healthcare professional with questions about your care.
Three Ways to Understand Your Glucose
A1c, GMI, and fructosamine look at glucose in different ways and over different periods of time.
A1c: The Longer View
Time covered: About 2–3 months.
A blood test that measures glucose attached to hemoglobin in red blood cells. It helps track long-term diabetes control.
Remember: Anemia, recent blood loss or transfusion, and certain conditions affecting red blood cells can make A1c less reliable.
GMI: Your Sensor’s Estimate
Time covered: The dates included in your continuous glucose monitor (CGM) report, often 14 days.
Glucose Management Indicator (GMI) converts your average sensor glucose into an A1c-like percentage. It is calculated from CGM readings rather than measured in a blood sample.
Remember: GMI and laboratory A1c may differ. For a useful CGM assessment, aim for at least 14 days of data with the sensor active at least 70% of the time.
Fructosamine: The Recent View
Time covered: About 2–4 weeks.
A blood test that measures glucose attached to proteins in the blood, mainly albumin. It can help assess recent glucose changes or monitor diabetes when A1c is unreliable.
Remember: Fructosamine is usually reported in µmol/L, rather than a percentage. Conditions affecting blood protein levels or turnover can affect its interpretation.
Why Might My Results Differ?
These measures cover different time periods. After a recent treatment change, GMI or fructosamine may show improvement before A1c does.
Red blood cell differences can affect A1c; blood protein changes can affect fructosamine; missing or inaccurate sensor readings can affect GMI.
A difference does not automatically mean one result is wrong. Your clinician will compare the results with your glucose readings and health history.
Look Beyond the Average
Averages can hide high and low glucose episodes. Your CGM report also shows time in range, time below range, and daily glucose patterns.
Review these together with your healthcare team before changing treatment.
Patient education • Reviewed October 10, 2026
Sources: American Diabetes Association, Standards of Care in Diabetes—2026; NIDDK, The A1C Test & Diabetes.
