Diabetes is be diagnosed by a three different types of blood tests:
- A1C - measures the average blood glucose levels for the last 3 months; no fasting required
- Normal < 5.7%
- Pre-diabetes: 5.7-6.4%
- Diabetes: >= 6.5%
- Fasting glucose - nothing to eat or drink (except water) for at least 8 hours prior to the test
- Normal: < 100 mg/mL
- Pre-diabetes: 100 - 125 mg/mL
- Diabetes: 126 mg/mL
- Oral glucose tolerance test (OGTT) - checks your blood sugar levels before and two hours after you drink a special sweet drink
- Fasting glucose levels as above
- Two hour glucose levels:
- Normal: less than 140 mg/dl
- Pre-diabetes: 140 mg/dl to 199 mg/dl
- Diabetes: 200 mg/dl or higher
In the United States, gestational diabetes is diagnosed using a “two step method”:
- One hour OGTT -non-fasting; checks your blood sugar level one hour after you drink a special sweet drink
- Normal: The American College of Obstetricians and Gynecologists recommends a 1 hour 50-gram screen-positive cut-off value of either 130 or 140 mg/dL
If the above test result is >= 130 mg/mL (or 140 mg/mL), the next step is to undergo a 3 hour OGTT.
- Fasting glucose level is obtained, followed by administration of a 75-g or 100-g glucose load, then evaluation of glucose levels after 1, 2, and often 3 hours. A diagnosis of gestational diabetes is made when 2 or more glucose values fall at or above the specified glucose thresholds.