Diagnosing diabetes

Diabetes usually is diagnosed with symptoms of increased thirst and urination. The doctor will do laboratory testing to determine if diabetes is the cause. 

Laboratory Tests for Diabetes 

1. A fasting blood sugar test can be performed after avoiding food and drinks for at least 8 hours. A fasting blood sugar level of >125 mg/dL is suggestive of diabetes. Fasting blood sugar level above 100mg/dL is considered abnormal and would be evidence of prediabetes.
2. A random blood glucose >200 mg/dL with symptoms of diabetes is suggestive of diabetes.
3. An oral glucose tolerance test (OGTT) can also be done to diagnose diabetes. An OGTT is done by fasting overnight followed by drinking a glucose-containing liquid in the morning. The blood glucose (BG) is measured before and 2 hours after the patient drinks the liquid. If the 2-hour blood glucose is >200 mg/dL, that is diagnostic of diabetes. If BG is between 140-199 mg/dL suggests prediabetes. If BG is <140 mg/dL is normal. 
4. A hemoglobin A1C is a blood test that measures what the average blood glucose level is over the past 3 months. You do not need to fast for this testing. An A1C of 6.5% or above is considered in diabetic range. 

To officially diagnoses diabetes the physician may perform 2 of the above tests on different days.