The purpose of screening is early diagnosis and treatment. Screening tests are usually administered to people without current symptoms, but who may be at high risk for certain diseases or conditions.

Screening Guidelines

Prediabetes is characterized by high blood glucose levels that are not high enough to be diagnosed as diabetes. The condition often progresses to type 2 diabetes.

In order to detect prediabetes and type 2 diabetes, the American Diabetes Association (ADA) recommends the following guidelines:

  • Screen adults of any age who are overweight or obese with one or more of these risk factors:     
  • First-degree relative with diabetes
  • Low high-density lipoprotein (HDL) (good) cholesterol level and high triglycerides levels
  • High blood pressure
  • History of diabetes during pregnancy (gestational diabetes) or having a baby weighing over nine pounds (4.1 kg)
  • Having polycystic ovary syndrome or other conditions associated with insulin resistance
  • Being inactive
  • History of cardiovascular disease
  • Belonging to an at-risk ethnic group (African American, Hispanic, Native American, Hispanic American, Asian American, or Pacific Islander)
  • Previous blood test results that show HbA1c levels at 5.7% or higher, impaired glucose tolerance, and impaired fasting glucose
  • Screen adults aged 45 and older with or without risk factors
  • Screen overweight children aged 10 years and older who have 2 or more of the following risk factors:     
  • Family history of diabetes
  • Mother with diabetes or gestational diabetes
  • Signs of insulin resistance or having a condition associated with insulin resistance
  • At-risk ethnic background
  • If the results are normal for both adults and children, the ADA recommends screening again in 3 years.

    Screening Tests

    HbA1c Test

    The HbA1c test is a good indicator of your average blood glucose levels over the past 2-4 months. This test usually does not require any dietary restrictions.

    DiagnosisHbA1c Level
    Diabetes6.5% or higher

    Fasting Plasma Glucose

    With this blood test, you need to fast (not eat anything) for at least 8 hours before the test.

    DiagnosisFasting Plasma Glucose Level
    Prediabetes100-125 mg/dL (5.6-6.9 mmol/L)
    Diabetes126 mg/dL (7 mmol/L) or higher

    Two-Hour Oral Glucose Tolerance Test

    After fasting overnight, the doctor tests your glucose level. You are then asked to drink 75 grams of glucose dissolved in water. Two hours later, the doctor tests your glucose level again.

    DiagnosisGlucose Levels
    Prediabetes140-199 mg/dL (7.8-11 mmol/L)
    Diabetes200 mg/dL (11.1 mmol/L) or higher


    Diabetes mellitus type 2. EBSCO DynaMed website. Available at: Updated July 29, 2013. Accessed August 28, 2013.

    Diabetes statistics. American Diabetes Association website. Available at: Accessed August 28, 2013.

    Glucose. Lab Tests Online website. Available at: Updated March 23, 2012. Accessed August 28, 2013.

    Prediabetes. EBSCO DynaMed website. Available at: Updated July 18, 2013. Accessed August 28, 2013.

    2/15/2010 DynaMed's Systematic Literature Surveillance American Diabetes Association. Standards of medical care in diabetes—2010. Diabetes Care. 2010;33 Suppl 1:S11-S61.

    2/15/2010 DynaMed's Systematic Literature Surveillance American Diabetes Association. Diagnosis and classification of diabetes mellitus. Diabetes Care. 2010;33 Suppl 1:S62-S69.

    Last reviewed September 2015 by Kim A. Carmichael, MD, FACP

    Please be aware that this information is provided to supplement the care provided by your physician. It is neither intended nor implied to be a substitute for professional medical advice. CALL YOUR HEALTHCARE PROVIDER IMMEDIATELY IF YOU THINK YOU MAY HAVE A MEDICAL EMERGENCY. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with any questions you may have regarding a medical condition.