In the United States, about 7 million people have undiagnosed diabetes, representing nearly one-fourth of all diabetes cases. Approximately 35% of adults aged 20 and older—or 79 million Americans—have prediabetes, a condition in which patients have blood glucose levels higher than normal but not high enough to be classi­fied as diabetes. These people are at increased risk of developing type 2 diabetes, heart disease, and stroke. “Clinicians should have a high index of suspicion for undiagnosed diabetes in people who are older, obese, physically inactive, or have a history of abnormal glucose tolerance, including gestational diabetes,” explains Robert E. Ratner, MD. Those with hypertension, dyslipidemia, and a family history of diabetes are also at high risk. Furthermore, racial and ethnic minorities have been shown to be at greater risk for diabetes. In people with these risk factors, periodic glucose testing should be performed to evaluate their dia­betes status.

“We need to identify people with prediabetes so that preventive measures can be undertaken.”

“The movement toward screening for diabetes in people without symptoms has become increas­ingly important because of the growing number of cases of undiagnosed diabetes and prediabetes,” explains Dr. Ratner. “To decrease the burden of the diabetes and obesity epidemics, clinicians need to diagnose patients as early as possible so that treatments can be administered early and so that diabetes-related complications can be man­aged and perhaps avoided. We need to identify people with prediabetes so that preventive mea­sures can be undertaken. The greatest opportunity for case-finding is in the clinical setting.”

Type 2 Diabetes & Future Disease

According to the American Diabetes Association’s Standards of Medical Care in Diabetes—2011, type 2 diabetes is frequently not diagnosed until complications appear. “Unfortunately, the effec­tiveness of mass testing asymptomatic individu­als for diabetes has not been proven definitively in clinical investigations,” Dr. Ratner says. “However, mathematical modeling studies sug­gest that screening people for diabetes at age 30 to 45 appears to be highly cost-effective.”

Dr. Ratner says there is frequently a long pre-symptomatic phase before a diagnosis of type 2 diabetes is made, and notes that clinicians now have simple tests at their disposal to detect preclinical disease. “As many as 20% of people presenting with a new diagnosis of diabetes will already have diabetic microvascular complica­tions, suggesting the disease has been present for 8 to 11 years. Effective interventions are available to prevent the progression of prediabetes to diabetes and to reduce risk of complications of the disease. The key is to offer screening and interventions to appropriate asymptomatic patients.”

The American Diabetes Association provides criteria for testing for diabetes in asymptomatic undiagnosed adults (Table 1). Testing should be considered in adults of any age who are considered clinically over­weight (based on BMI) and have one or more known risk factors for diabetes. Testing of people without other diabetes risk factors should begin no later than age 45, according to the American Diabetes Association, because age has been identified as a major risk factor for the disease.

Assessing Diabetes Testing Strategies

The A1C, fasting plasma glucose, and 2-hour oral glucose tests have been deemed appropriate diabetes tests for asymptomatic and symptomatic individuals by the American Diabetes Association. These tests can give clinicians a good indication of who has diabetes or prediabetes. Abnormal results should trigger regular follow-up and discussion with patients.

Community screening of diabetes outside health­care settings is not currently recommended because people with positive tests may not have access to care or seek the follow-up testing and care they need. There may also be failure to ensure appropriate repeat testing for individuals who test negative. Furthermore, such screening may fail to reach the groups most at risk and inap­propriately test those at low risk. The appropriate interval between tests is currently unknown, adds Dr. Ratner. “The rationale for the 3-year interval is that there is little likelihood that an individual will develop significant complications of diabetes within 3 years of a negative test result. Also, repeat screenings every 3 or 5 years have been deemed cost-effective in modeling analyses.”

Testing for Type 2 Diabetes in Children

The incidence of obesity and type 2 diabetes in adolescents has increased dramatically in the last decade, especially in minority populations. The American Diabetes Association provides recom­mendations for testing for type 2 diabetes in high-risk children (Table 2). While type 2 disease is rel­atively rare in the general pediatric population, it is important to consider these patients for testing. Dr. Ratner says “the diabetes and obesity burden continues to grow, but identifying younger people who are at risk may perhaps alleviate some of this burden in the future.”


American Diabetes Association. Standards of Medical Care in Diabetes—2011. Diabetes Care. 2011;34:S11-S61. Available at:

Kahn R, Alperin P, Eddy D, et al. Age at initiation and frequency of screening to detect type 2 diabetes: a cost-effectiveness analysis. Lancet. 2010;375:13651374.

Tuomilehto J, Lindström J, Eriksson JG, et al. Finnish Diabetes Prevention Study Group. Prevention of type 2 diabetes mellitus by changes in lifestyle among subjects with impaired glucose tolerance. N Engl J Med. 2001;344:13431350.

Diabetes Prevention Program Research Group. 10 year follow-up of diabetes incidence and weight loss in the Diabetes Prevention Program Outcomes Study. Lancet. 2009;374:1677-1686.

Johnson SL, Tabaei BP, Herman WH. The efficacy and cost of alternative strategies for systematic screening for type 2 diabetes in the U.S. population 45–74 years of age. Diabetes Care. 2005;28:307311.