Diagnosis of diabetes

Diagnosis of diabetes involves one of three diabetes tests:  a fasting plasma glucose test (FPG), oral glucose tolerance (OGTT) or an A1C test.

Fasting plasma glucose test (FPG) involves the person going without food overnight and having blood drawn the first thing in the morning.  A normal FPG test is 100 mg/dL.  A FPG result of 100 to 125 mg/dL is considered prediabetes.  A FPG result above 126 mg/dL points to diabetes.

Oral glucose tolerance test (OGTT) involves the person fasting overnight.  The person’s blood sugar is drawn the first thing in the morning.  This person drinks a glucose-rich drink and a second blood sugar specimen is drawn 2 hours after drinking the drink.  Normal blood glucose for a OGTT is below 140 mg/dL.  If the result of this test is between 140 and 199, the person has prediabetes.  A blood sugar result above 200 mg/dL diagnoses diabetes. 

A1C measures the amount of blood sugar present in the blood for the past 3-4 months.  An A1C of 5.6  or below is considered normal.  A level of 5.7 to 6.4% is prediabetic.  An A1C level of 6.5% or above diagnoses diabetes.  Information about diagnosing diabetes can be found at http://www.diabetes.org/diabetes-basics/prevention/pre-diabetes/pre-diabetes-faqs.html