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How Diabetes Is Diagnosed

Diabetes Home

Diabetes Prevention and Control Program
275 East Main Street
Frankfort, KY  40621
(502) 564-7996

How Diabetes Is Diagnosed     

Symptoms of type 1 diabetes usually develop over a short period of time, although beta cell destruction can begin months, even years, earlier. Symptoms include increased thirst and urination, constant hunger, weight loss, blurred vision, and extreme fatigue. If not diagnosed and treated with insulin, a person can lapse into a life-threatening coma.

The symptoms of type 2 diabetes develop gradually and are not as noticeable as in type 1 diabetes. In fact, there may be no noticeable symptoms.  However, symptoms could include:

  • Feeling tired or ill
  • Frequent urination (especially at night)
  • Unusual thirst
  • Increased hunger
  • Weight loss
  • Blurred vision
  • Frequent infections
  • Slow-healing wounds and sores
  • Tingling/numbness in hands or feet
  • Sexual Dysfunction

In 2010, the American Diabetes Association added the recommended use of the A1C test to diagnose diabetes, with a threshold of 6.5 percent or higher. (Test performed in a laboratory using a method that is certified by the National Glycohemoglobin Standardization Program and standardized to the Diabetes Control and Complications Trial reference assay.) 

Criteria for Diagnosis of Pre-Diabetes

  1. Fasting* Plasma Glucose 100-125 mg/dl = Impaired Fasting Glucose (IFG)
  2. 2 hour post 75g oral glucose challenge 140-199 mg/dl = Impaired Glucose Tolerance (IGT)
  3. A1C 5.7 percent - 6.4 percent

*Fasting is no intake of calories for at least 8 hours.

Criteria for Diagnosis of Diabetes

  1. A1C 6.5 percent or higher
  2. Fasting plasma glucose 126 mg/dl or higher
  3. 2 hour plasma glucose (with a 75 g OGTT) 200 mg/dl or higher
  4. Random* plasma glucose 200 mg/dl or higher

*Random is any time of day without regard to time since last meal.

For criteria 1-3: Test should be repeated to confirm unless symptoms are present. It is preferable that the same test be repeated for confirmation, but if two different tests are used and both indicate diabetes, consider the diagnosis confirmed.


Last Updated 2/27/2014