What are the guidelines for diabetes screening and management?

Guidelines on Diabetes Screening

All adults should begin screening for prediabetes and type 2 diabetes at age 35 years, with earlier screening for those with overweight/obesity and additional risk factors. 1

Who Should Be Screened

Adults with Overweight or Obesity

Testing should be considered in adults with overweight or obesity (BMI ≥25 kg/m² or ≥23 kg/m² in Asian Americans) who have one or more of the following risk factors: 1

• First-degree relative with diabetes 1
• High-risk race/ethnicity (African American, Latino, Native American, Asian American, Pacific Islander) 1
• History of cardiovascular disease 1
• Hypertension (≥130/80 mmHg or on therapy) 1
• HDL cholesterol <35 mg/dL (0.90 mmol/L) and/or triglycerides >250 mg/dL (2.82 mmol/L) 1
• Polycystic ovary syndrome 1
• Physical inactivity 1
• Other insulin resistance conditions (severe obesity, acanthosis nigricans) 1

Universal Age-Based Screening

For all other adults without the above risk factors, screening should begin at age 35 years. 1 This represents an important update from older guidelines that recommended starting at age 45 years. 1 The rationale is that the number needed to screen drops sharply at age 35, from 80 in 30-34 year-olds to 31 in 35-39 year-olds. 2

Special Populations Requiring Screening

Consider screening individuals on certain medications: 1

• Glucocorticoids 1
• Statins 1
• Thiazide diuretics 1
• Some HIV medications 1

Women with gestational diabetes history require lifelong screening at least every 3 years. 1

Screening Frequency

If initial screening results are normal, repeat testing at minimum 3-year intervals is reasonable. 1 However, more frequent screening should be considered sooner with symptoms or change in risk factors such as weight gain. 1

People with prediabetes (A1C 5.7-6.4%, impaired fasting glucose, or impaired glucose tolerance) should be tested yearly. 1

Screening Tests

Three tests are equally appropriate for screening: fasting plasma glucose (FPG), 2-hour plasma glucose during 75-g oral glucose tolerance test (OGTT), and HbA1c. 1, 3 Each has distinct advantages and limitations:

Fasting Plasma Glucose

• Requires 8-hour fast 3
• Diabetes diagnosis: ≥126 mg/dL (7.0 mmol/L) 3
• Prediabetes (impaired fasting glucose): 100-125 mg/dL (5.6-6.9 mmol/L) 3
• Poor preanalytical stability; plasma should be separated immediately or samples kept on ice 3

2-Hour OGTT

• Requires adequate carbohydrate intake (at least 150 g/day) for 3 days prior to testing 1, 3
• Diabetes diagnosis: ≥200 mg/dL (11.1 mmol/L) at 2 hours 3
• Prediabetes (impaired glucose tolerance): 140-199 mg/dL (7.8-11.0 mmol/L) at 2 hours 3
• Diagnoses more people with prediabetes and diabetes compared to FPG and HbA1c cutoffs 3

HbA1c

• Diabetes diagnosis: ≥6.5% (48 mmol/mol) 3
• Prediabetes: 5.7-6.4% (39-47 mmol/mol) 3
• Greater convenience (no fasting required) and better preanalytical stability than glucose tests 3
• Must be performed using NGSP-certified method standardized to DCCT assay 3
• Should not be used in conditions with increased red blood cell turnover: anemia, hemoglobinopathies, pregnancy, hemodialysis, recent blood loss or transfusion, or erythropoietin therapy 3

Important Caveat on Test Concordance

The concordance between different screening tests is imperfect. 3 HbA1c and glucose-based tests may yield discordant results. In individuals with discordant values, fasting glucose and 2-hour glucose tests are more accurate. 3 This means some patients may screen positive on one test but negative on another—when in doubt, use glucose-based testing for confirmation.

Pediatric Screening

Risk-based screening should be considered after the onset of puberty or after 10 years of age, whichever occurs earlier, in children and adolescents with overweight (BMI ≥85th percentile) or obesity (BMI ≥95th percentile) who have one or more risk factors: 1

• Maternal history of diabetes or gestational diabetes during the child's gestation 1
• Family history of type 2 diabetes in first- or second-degree relative 1
• High-risk race/ethnicity (Native American, African American, Latino, Asian American, Pacific Islander) 1
• Signs of insulin resistance or associated conditions (acanthosis nigricans, hypertension, dyslipidemia, polycystic ovary syndrome, small-for-gestational-age birth weight) 1

If tests are normal, repeat screening at minimum 3-year intervals, or more frequently if BMI is increasing or risk factor profile deteriorating. 1

Screening for Type 1 Diabetes

Screening for type 1 diabetes risk through islet autoantibody testing can effectively identify individuals who will develop type 1 diabetes. 1 Multiple studies show that individuals who develop more than two autoantibodies have nearly 70% risk of developing type 1 diabetes within 10 years and 84% within 15 years. 1 However, routine population-based screening for type 1 diabetes is not currently recommended outside of research programs or high-risk family members. 1

Critical Implementation Points

All screening should be done as part of a healthcare office visit, not as standalone community screening. 1 Positive test results should be confirmed on another day, except when random plasma glucose is ≥200 mg/dL with classic symptoms of hyperglycemia (polyuria, polydipsia, unexplained weight loss). 3, 4

Plasma glucose must be measured in an accredited laboratory when used for diagnosis or screening. 1 For glucose samples, use tubes containing rapidly effective glycolytic inhibitor such as granulated citrate buffer; tubes with only sodium fluoride should not be relied upon to prevent glycolysis. 1

The U.S. Preventive Services Task Force provides a Grade B recommendation for screening adults aged 35-70 years with overweight or obesity, emphasizing that clinicians should offer or refer patients with prediabetes to effective preventive interventions. 5 This aligns closely with American Diabetes Association guidelines but with a narrower age range. 5