Fasting Blood Sugar (FBS): An indicator for diabetes mellitus and insulin resistance if elevated
Goal values:
- Less than 100 mg/dL
- 110-125 mg/dL = impaired fasting glucose
- Greater than 126 mg/dL = diabetes
Preparation
This test requires a 12-hour fast. You should wait to eat and/or take a hypoglycemic agent (insulin or oral medication) until after test has been drawn, unless told otherwise.
Eating and digesting foods called carbohydrates forms glucose (blood sugar). Glucose is needed by your body to provide energy to carry out your normal activities. Insulin is needed by the body to allow glucose to go into the cells and be used as energy. Without insulin, the levels of glucose in the blood will rise. Diabetes is a disease that occurs when either the pancreas (an organ in your body) is not able to produce insulin or the pancreas makes insulin, but it does not work as it should. Fasting blood sugar is a part of diabetic evaluation and management. An FBS greater than 126 mg/dl on more than one occasion usually indicates diabetes.
Glycosylated Hemoglobin or Hemoglobin A1C (HbA1C): Reflects average blood sugar levels over the preceding 2-3 month period
Goal values:
- Normal adult: less than 6.0%
- Diabetic adult: less than 7.0%
Preparation
This test may be measured any time of the day without fasting.
Glycosylated hemoglobin is blood glucose attached to hemoglobin (a component of blood). This test is often called the "diabetic report card." It reflects the average blood sugar for the two to three month period before the test.
To calculate the average blood glucose level from the HbA1C:
HbA1C level x (multiplied by) 33.3 – 86 = average blood glucose level for the past 90 days. HbA1C can be helpful to track diabetic control over time.
