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 percent 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.
| Type of test | Normal | Pre-diabetes | Diabetes |
|---|---|---|---|
| Fasting glucose test | Less than 100 | 100-125 | 126 or higher |
| Random (anytime) glucose test | Less than 140 | 140-199 | 200 or higher |
| A1c test | Less than 5.7% | 5.7 - 6.4% | 6.5% or higher |
