A1C to eAG Calculator
Use this calculator to convert your A1C percentage to an estimated average glucose (eAG) level, or vice versa.
Calculate eAG from A1C
Calculate A1C from eAG
Understanding the A1C Calculation Formula and Your Blood Sugar
The A1C test, also known as the hemoglobin A1c, HbA1c, or glycated hemoglobin test, is a crucial blood test used to diagnose and monitor diabetes. Unlike daily blood glucose readings that show your sugar levels at a specific moment, the A1C test provides an average of your blood sugar levels over the past two to three months.
What is A1C?
Hemoglobin is a protein found in red blood cells that carries oxygen throughout your body. When glucose (sugar) enters your bloodstream, it attaches to hemoglobin. This process is called glycation. The more sugar in your blood, the more hemoglobin gets glycated. Red blood cells live for about three months, so the A1C test measures the percentage of your hemoglobin that is coated with sugar, reflecting your average blood sugar control over that period.
What is Estimated Average Glucose (eAG)?
While A1C is expressed as a percentage, many people find it easier to understand their blood sugar levels in the same units they use for daily glucose monitoring (mg/dL or mmol/L). This is where Estimated Average Glucose (eAG) comes in. eAG is a calculated value that converts your A1C percentage into an average blood glucose level, making it more relatable to your daily readings.
The A1C to eAG Calculation Formula
The relationship between A1C and eAG is well-established and is based on a formula derived from clinical studies. The most commonly accepted formula, endorsed by organizations like the American Diabetes Association (ADA), is:
eAG (mg/dL) = (28.7 × A1C) – 46.7
This formula allows healthcare providers and individuals to translate an A1C percentage directly into an average blood glucose value, providing a clearer picture of long-term glucose control.
Converting eAG back to A1C
Conversely, if you know your estimated average glucose and want to find the corresponding A1C percentage, you can rearrange the formula:
A1C (%) = (eAG (mg/dL) + 46.7) / 28.7
This conversion is useful for understanding what a certain average blood sugar level means in terms of your A1C target.
Why are these calculations important?
- Monitoring Diabetes: For individuals with diabetes, A1C and eAG are vital tools for monitoring the effectiveness of their treatment plan. Regular testing helps determine if blood sugar levels are within a healthy range and if adjustments to medication, diet, or exercise are needed.
- Diagnosis: A1C is also used to diagnose prediabetes and type 2 diabetes.
- Normal: Below 5.7% (eAG below 117 mg/dL)
- Prediabetes: 5.7% to 6.4% (eAG 117-137 mg/dL)
- Diabetes: 6.5% or higher (eAG 140 mg/dL or higher)
- Patient Education: Presenting A1C results as eAG can help patients better understand their long-term glucose control in terms of their daily blood sugar numbers, fostering better self-management.
Realistic Examples
Let's look at some practical applications of the A1C calculation formula:
Example 1: Calculating eAG from a typical A1C
Suppose your A1C test result is 7.0%. Using the formula:
eAG (mg/dL) = (28.7 × 7.0) – 46.7
eAG (mg/dL) = 200.9 – 46.7
eAG (mg/dL) = 154.2 mg/dL
To convert to mmol/L: 154.2 / 18 = 8.6 mmol/L
So, an A1C of 7.0% corresponds to an estimated average glucose of approximately 154 mg/dL or 8.6 mmol/L.
Example 2: Calculating A1C from an average glucose level
Imagine your average daily blood glucose readings over the past few months have been around 120 mg/dL. What A1C would this correspond to?
A1C (%) = (120 + 46.7) / 28.7
A1C (%) = 166.7 / 28.7
A1C (%) = 5.8%
An average glucose of 120 mg/dL would typically result in an A1C of about 5.8%, which falls into the prediabetes range.
Understanding these calculations empowers you to better interpret your test results and work with your healthcare team to manage your blood sugar effectively.