Fasting glucose is a measure of blood glucose levels after an overnight fast (usually at least 8 hours). A fasting blood sugar of less than 100 mg/dL is normal. A fasting blood sugar of 100 to 125 mg/dL is considered prediabetes. A value of 126 mg/dL or higher on two separate occasions is diagnostic for diabetes.
Hemoglobin A1c, or glycated hemoglobin, is a blood test that represents an estimate of blood glucose levels over the previous 2-3 months. Hemoglobin is responsible for binding oxygen for transport throughout the body. Hemoglobin can also bind glucose, which is more pronounced when glucose levels are elevated. The hemoglobin becomes glycated and remains in circulation for the remainder of its 120-day lifecycle.
The A1c represents the percentage of hemoglobin that is glycated. This test can be used to screen for diabetes as well as to monitor treatment response.
