Diabetes Diagnosis

To schedule an appointment with a diabetes specialist or for more information regarding the diagnosis of diabetes, please call 314.747.9355 or toll-free 877.747.9355 or email us.

There are several ways to diagnose diabetes. A diagnosis of diabetes is made when any one of these tests is positive. Each test is usually repeated on a second day to confirm the diagnosis.

  • A1C: The A1C test measures your average blood glucose level for the past 2 – 3 months. This test does not require you to fast or drink anything. Diabetes is diagnosed at an A1C of greater than or equal to 6.5%.
  • Fasting plasma glucose (FPG): This test measures your blood glucose levels after a period of fasting. Because the test requires you to not eat or drink anything (except water) for at least eight hours before the test, it is usually done first thing in the morning. Diabetes is diagnosed at a fasting blood glucose level of greater than or equal to 126 mg/dl.
  • Casual (also called random) plasma glucose test: This test can be taken at any time of the day when you have severe diabetes symptoms. Diabetes is diagnosed at a blood glucose level of greater than or equal to 200 mg/dl.
  • Oral glucose tolerance test (OGTT): The OGTT is obtained two hours after a drink containing glucose has been consumed, which occurs after fasting for at least eight hours. Diabetes is diagnosed at two hour blood glucose level of greater than or equal to 200 mg/dl.

Prediabetes Diagnosis

Prediabetes is a condition when your blood glucose is higher than normal but not high enough to be diabetes. This condition puts you at a higher risk for developing type 2 diabetes.

The same tests used to diagnose diabetes are used to diagnose prediabetes. Results indicating prediabetes are:

  • An A1C of 5.7% - 6.4%.
  • Fasting blood glucose level of 100 mg/dl – 125 mg/dl.
  • An OGTT two hour blood glucose level of 140 mg/dl – 199 mg/dl.

Gestational Diabetes Diagnosis

Gestational diabetes may be diagnosed with one of two approaches:

  • A 75-gram glucose screening test, which involves drinking a glucose drink followed by measurement of the blood sugar level after two hours. This test is done at 24 to 28 weeks gestation. 
  • A 50-gram glucose screening test, which is followed by a diagnostic 100-gram glucose tolerance test in those women whose blood sugar equals or exceeds 130 mg/dL one hour after the initial screening test

Diagnosing Diabetes

According to the National Institute of Diabetes and Digestive and Kidney Diseases:

  • People over age 45 should be tested for prediabetes or diabetes. If the first blood glucose test is normal, they should be retested every three years.
  • People under age 45 should consider getting tested for prediabetes or diabetes if they have a body mass index (BMI) of greater than or equal to 25 kgm/m2 and have one or more of the following risk factors:
    • Having a first-degree relative with diabetes (mother, father, or sibling)
    • Being a member of a high-risk ethnic group (African-American, Hispanic, Asian, Pacific Islander, or Native American)
    • Delivering a baby weighing more than 9 pounds, or having diabetes during pregnancy
    • Having blood pressure at or above 140/90 mm/Hg
    • Having abnormal blood fat levels, such as high-density lipoproteins (HDL) less than or equal to 35 mg/dL, or triglycerides greater than or equal to 250 mg/dL (mg/dL = milligrams of glucose per deciliter of blood)
    • Having a sedentary lifestyle
    • Having impaired glucose tolerance when previously tested for diabetes
    • Having polycystic ovarian syndrome

To schedule an appointment with a diabetes specialist or for more information regarding the diagnosis of diabetes, please call 314.747.9355 or toll-free 877.747.9355.