Finding diabetes can help to decrease complications. It may also find a condition called prediabetes. This is a blood glucose level that is high but not yet diabetes. It will often move on to type 2 diabetes. Finding it early may help to prevent diabetes from starting.

Screening tests are given to people who may be at high risk.

Screening Guidelines

American Diabetes Association (ADA) recommends screening for prediabetes and type 2 diabetes in the following:

  • Adults who are overweight or obese with one or more of these risk factors:
    • First-degree relative with diabetes
    • High-risk group (African American, Latino, Native American, Hispanic American, Asian American, or Pacific Islander)
    • History of cardiovascular disease
    • High blood pressure
    • Low high-density lipoprotein (HDL) (good) cholesterol level and high triglycerides levels
    • Polycystic ovary syndrome
    • Inactive lifestyle
    • Other conditions that can cause insulin resistance such as severe obesity, acanthosis nigricans
  • Women who have had gestational diabetes
  • Anyone with previous prediabetes
  • Adults aged 45 and older with or without risk factors
  • Overweight children over 10 years old (or after puberty starts) with 1 or more of these risk factors:
    • High body mass index (BMI) based on child's weight and height
    • Family history of any type of diabetes, including during pregnancy
    • Signs of insulin resistance or having a condition associated with insulin resistance
    • At-risk ethnic background

Screening may be repeated 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

American Diabetes Association. Standards of medical care in diabetes-2018. Diabetes Care. 2018 Jan; 41(Suppl 1):S1-172 PDF. Available at: Accessed December 3, 2018.

Diabetes mellitus type 2 screening. EBSCO DynaMed Plus website. Available at: Updated November 12, 2018. Accessed December 3, 2018.

Prediabetes. EBSCO DynaMed Plus website. Available at: Updated November 16, 2018. Accessed December 3, 2018.

8/2/2019 EBSCO DynaMed website. Available at: DynaMed Systematic Literature Surveillance American Diabetes Association. 2. Classification and Diagnosis of Diabetes: Standards of Medical Care in Diabetes-2019. Diabetes Care. 2019;42(Suppl 1):S13-S28.

Last reviewed December 2018 by James P. Cornell, MD  Last Updated: 8/2/2019