Tests & Procedures



Diagnosing Diabetes

Protocol for 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

A diagnosis of diabetes

A diagnosis of diabetes is made when any one of these tests is positive. The result may be confirmed by a second positive test on a different day:

  • A1C greater than or equal to 6.5 percent
  • Fasting plasma glucose of greater than or equal to 126 mg/dL
  • Casual plasma glucose (taken at any time of the day) of greater than or equal to 200 mg/dL with the symptoms of diabetes
  • Oral glucose tolerance test (OGTT) value of greater than or equal to 200 mg/dL. The OGTT is obtained 2 hours after a drink containing gludose has been consumed, which occurs after fasting for at least eight hours.

A diagnosis of gestational diabetes

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

Consult your doctor regarding your wish to be screened for gestational diabetes.

Click here to view the
Online Resources of Diabetes

Last reviewed: 4/26/2013