Health Library

Health Library

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 3 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 kg/m2 and have 1 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 1 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%

  • 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 glucose has been consumed, which occurs after fasting for at least 8 hours.

A diagnosis of gestational diabetes

Gestational diabetes may be diagnosed with 1 of 2 approaches:

  • A 75-gram glucose screening test, which involves drinking a glucose drink followed by measurement of the blood sugar level after 2 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 1 hour after the initial screening test

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

Diagnosing Diabetes - WellSpan Health

Online Medical Reviewer: Grantham, Paula, RN, BSN
Online Medical Reviewer: MMI board-certified, academically affiliated clinician
© 2014 WellSpan Health. All Rights Reserved. This information is not intended as a substitute for professional medical care. Always follow your healthcare professional's instructions.

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