What are the current guidelines for screening, diagnosing, and managing diabetes mellitus in adults, including lifestyle modification, pharmacologic therapy, glycemic targets, monitoring frequency, and cardiovascular risk management?

Guidelines for Diabetes Mellitus Management in Adults

All adults should begin screening for diabetes at age 35 years using fasting plasma glucose, HbA1c, or 2-hour oral glucose tolerance test, with earlier screening for those with overweight/obesity and additional risk factors. 1

Screening Recommendations

Who to Screen

• Adults with overweight or obesity (BMI ≥25 kg/m² or ≥23 kg/m² in Asian Americans) plus one or more risk factors: first-degree relative with diabetes, high-risk race/ethnicity, cardiovascular disease history, hypertension, dyslipidemia, polycystic ovary syndrome, or physical inactivity 1
• Adults with hypertension or hyperlipidemia should be screened regardless of other factors, as detecting diabetes substantially improves cardiovascular risk stratification and management 2

Screening Frequency

• Repeat testing every 3 years if initial results are normal, with more frequent screening if weight gain or new symptoms develop 1
• Annual testing for patients with prediabetes (fasting glucose 100-125 mg/dL or HbA1c 5.7-6.4%) 1

Diagnostic Tests

Three tests are equally appropriate for diagnosis 1:

• Fasting plasma glucose ≥126 mg/dL (requires 8-hour fast) 2, 1
• HbA1c ≥6.5% (no fasting required, most convenient) 1, 3
• 2-hour oral glucose tolerance test ≥200 mg/dL (requires 75g glucose load) 1
• Random plasma glucose ≥200 mg/dL with classic symptoms (polyuria, polydipsia, weight loss) establishes diagnosis without confirmation 3

All positive screening tests must be confirmed on a separate day, except when random glucose ≥200 mg/dL with hyperglycemic symptoms 1. Plasma glucose must be measured in an accredited laboratory using tubes with glycolytic inhibitor 1.

Management of Prediabetes

Lifestyle Intervention (First-Line)

• Prescribe at least 150 minutes per week of moderate-intensity aerobic activity (approximately 700 kcal/week energy expenditure) 4
• Add resistance training at least 2 times per week 4
• Implement Mediterranean or DASH eating pattern emphasizing whole grains, legumes, nuts, fruits, vegetables with minimal processed foods 4
• Break up prolonged sedentary time to lower postprandial glucose 4

Pharmacologic Therapy

• Consider metformin for high-risk patients: BMI ≥35 kg/m² or age <60 years with prediabetes 4
• Metformin has the strongest evidence base and long-term safety for diabetes prevention 4

Monitoring

• Annual diabetes screening with fasting glucose or HbA1c, as approximately 10% progress to diabetes annually 4
• Reassess lifestyle adherence every 3-6 months 4

Management of Type 2 Diabetes

Initial Pharmacologic Therapy

• Initiate metformin at diagnosis unless contraindicated 5
• Verify adequate renal function before starting: serum creatinine <1.5 mg/dL in men or <1.4 mg/dL in women 5
• Measure serum creatinine at least annually and with any dose increase 5

Glycemic Targets

• Target HbA1c <7.0% for most adults to reduce microvascular complications 5
• Recheck HbA1c at 3 months; if target not achieved, add second agent 5

Treatment Escalation Algorithm

When metformin monotherapy is insufficient:

• If HbA1c ≥9.0%, add basal insulin for most robust glucose lowering 5
• Consider GLP-1 receptor agonist for additional weight loss and cardiovascular protection 5
• Avoid sulfonylureas in older adults due to prolonged half-life and hypoglycemia risk 5

Lifestyle Modifications

• Limit sodium intake to <2,300 mg/day 5
• Avoid sugar-sweetened beverages entirely 5
• Engage in ≥150 minutes per week of moderate-to-vigorous aerobic activity, spread over at least 3 days with no more than 2 consecutive days without activity 5
• Reduce saturated fat, trans fat, and cholesterol intake; increase omega-3 fatty acids, viscous fiber, and plant stanols/sterols 2

Cardiovascular Risk Management

Blood Pressure Management

• Measure blood pressure at every routine diabetes visit 2
• Target systolic blood pressure <130 mmHg and diastolic <80 mmHg 2
• For blood pressure 130-139/80-89 mmHg, trial lifestyle therapy for maximum 3 months, then add pharmacologic agents if targets not achieved 2
• For blood pressure ≥140/90 mmHg, initiate pharmacologic therapy immediately in addition to lifestyle therapy 2
• Lifestyle therapy includes weight loss if overweight, DASH-style diet, sodium reduction, potassium increase, alcohol moderation, and increased physical activity 2

Lipid Management

• Measure fasting lipid profile at least annually (every 2 years if low-risk: LDL <100 mg/dL, HDL >50 mg/dL, triglycerides <150 mg/dL) 2

Statin therapy should be added to lifestyle therapy, regardless of baseline lipid levels, for:

• All diabetic patients with overt cardiovascular disease 2
• Patients without cardiovascular disease who are over age 40 with one or more cardiovascular risk factors 2

Lipid targets:

• Primary goal: LDL cholesterol <100 mg/dL in individuals without overt cardiovascular disease 2
• Optional lower goal: LDL <70 mg/dL using high-dose statin in individuals with overt cardiovascular disease 2
• Alternative goal: 30-40% reduction in LDL from baseline if targets not reached on maximal tolerated statin 2

Immunizations

• Annual influenza vaccine for all diabetic patients ≥6 months of age 2
• Pneumococcal polysaccharide vaccine for all diabetic patients ≥2 years of age, with one-time revaccination for those <64 years if previously immunized when <65 years and vaccine was administered >5 years ago 2
• Hepatitis B vaccination per CDC recommendations 2

Special Populations

Pediatric Screening

• Risk-based screening after puberty onset or after age 10 years (whichever is earlier) in children/adolescents with overweight or obesity plus one or more risk factors: maternal diabetes history, family history of type 2 diabetes, high-risk race/ethnicity, or signs of insulin resistance 1

End-of-Life Care

For older adults receiving palliative or hospice care 2:

• Stable patients: Continue previous regimen focusing on hypoglycemia prevention, keeping glucose below renal threshold; minimal role for HbA1c monitoring 2
• Patients with organ failure: Preventing hypoglycemia is paramount; for type 1 diabetes, reduce but do not stop insulin as oral intake decreases; for type 2 diabetes, titrate agents causing hypoglycemia 2
• Dying patients: For type 2 diabetes, discontinuation of all medications may be reasonable; for type 1 diabetes, small amount of basal insulin may prevent acute hyperglycemic complications 2

Common Pitfalls to Avoid

• Do not rely on random capillary blood glucose for screening, as it is less well standardized despite reasonable sensitivity 2
• Do not use HbA1c alone in patients with hemoglobinopathies or conditions affecting red blood cell turnover; confirm with plasma glucose testing 1
• Do not perform community-based screening; all screening should occur as part of healthcare office visits 1
• Do not assume tight glycemic control reduces macrovascular complications; existing studies have not demonstrated this benefit 2