A1C Estimation for Fasting Glucose of 130 mg/dL
A fasting glucose of 130 mg/dL corresponds to an estimated A1C of approximately 6.5-7.0%. 1
Direct Conversion Data
Based on the ADAG (A1C-Derived Average Glucose) trial data from the American Diabetes Association guidelines, the relationship between fasting glucose and A1C has been empirically established:
- For an A1C of 6.5-6.99%: The average fasting glucose is 142 mg/dL (95% CI: 135-150) 1, 2
- For an A1C <6.5%: The average fasting glucose is 122 mg/dL (95% CI: 117-127) 1, 2
Since your fasting glucose of 130 mg/dL falls between these two ranges, the estimated A1C would be approximately 6.3-6.7%, closer to the lower end of the prediabetic/diabetic range. 1, 2
Alternative Estimation Formula
A simplified clinical formula suggests: (FBG + 80) ÷ 30 = estimated A1C 3
Using this approach:
- (130 + 80) ÷ 30 = 7.0% 3
This formula tends to slightly overestimate A1C compared to the more precise ADAG data, but provides a quick bedside calculation. 3
Important Clinical Caveats
Single fasting glucose measurements have limitations in predicting A1C because:
- A1C reflects average glucose over 2-3 months, incorporating fasting, premeal, postmeal, and bedtime values 1
- The ADAG correlation was based on approximately 2,700 glucose measurements over 3 months per A1C measurement 1, 4
- Fasting glucose alone accounts for only part of overall glycemic control 1
Conditions affecting accuracy include hemoglobin variants, hemolysis, and blood loss, which can alter A1C independent of glucose levels. 1
Clinical Significance
A fasting glucose of 130 mg/dL indicates:
- Impaired fasting glucose (100-125 mg/dL is prediabetes; ≥126 mg/dL is diabetes) 1
- This level places the patient at increased risk for diabetes and cardiovascular disease 1
- Intensive lifestyle interventions including weight loss and physical activity are warranted 1
The most accurate determination requires actual A1C measurement, which should be performed at least twice yearly in stable patients or quarterly when therapy changes or goals are not met. 1