Diabetes Mellitus: An Overview: Diagnosis and Tests

How is diabetes diagnosed?

Diabetes is diagnosed with fasting sugar blood tests or with A1c blood tests, also known as glycated hemoglobin tests. A fasting blood sugar test is performed after you have had nothing to eat or drink for at least eight hours. Normal fasting blood sugar is less than 100 mg/dl (5.6 mmol/l). You do not have to be fasting for an A1c blood test. Diabetes is diagnosed by one of the following (see chart):

• Your blood sugar level is equal to or greater than 126 mg/dl (7 mmol/l).
• You have two random blood sugar tests over 200 mg/dl (11.1 mmol/l) with symptoms.
• You have an oral glucose tolerance test with results over 200 mg/dl (11.1 mmol/l).
• Your A1c test is greater than 6.5% on two separate days.

An A1c test should be performed in a laboratory using a method that is certified by the National Glycohemoglobin Standardization Program (NGSP) and standardized to the Diabetes Control and Complications Trial (DCCT) assay.

• Fasting Glucose Test
  • Normal: Less than 100
  • Pre-diabetes: 100-125
  • Diabetes: 126 or higher
• Random (anytime) Glucose Test
  • Normal: Less than 140
  • Pre-diabetes: 140-199
  • Diabetes: 200 or higher
• A1c Test
  • Normal: Less than 5.7%
  • Pre-diabetes: 5.7 - 6.4%
  • Diabetes: 6.5% or higher