What are the current guidelines for screening, diagnosis, and comprehensive management of diabetes in adults (including treatment targets, pharmacologic therapy, lifestyle modification, and monitoring)?

Diabetes Guidelines: Screening, Diagnosis, and Management

Screening Recommendations

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 to Screen Earlier

Screen adults with BMI ≥25 kg/m² (≥23 kg/m² in Asian Americans) who have one or more of the following risk factors: 2, 1

• First-degree relative with diabetes 2
• High-risk race/ethnicity (African American, Latino, Native American, Asian American, Pacific Islander) 2
• History of cardiovascular disease 2
• Hypertension (≥140/90 mmHg or on antihypertensive therapy) 2
• HDL cholesterol <35 mg/dL or triglycerides >250 mg/dL 2
• Women with polycystic ovary syndrome 2
• Physical inactivity 2
• Other insulin resistance conditions (severe obesity, acanthosis nigricans) 2

Screening Frequency

• If initial results are normal: repeat every 3 years minimum 2, 1
• If prediabetes is diagnosed: test annually 2, 1
• Women with prior gestational diabetes: test at least every 3 years lifelong 2
• Consider more frequent screening with weight gain or symptom development 1

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Diagnostic Criteria

Diabetes is diagnosed when any of the following criteria are met (confirmation required on a separate day unless symptomatic): 3

Diabetes Diagnosis Thresholds

• Fasting plasma glucose ≥126 mg/dL (after 8-hour fast) 3
• 2-hour plasma glucose ≥200 mg/dL during 75-g oral glucose tolerance test 3
• HbA1c ≥6.5% (using NGSP-certified method) 3
• Random plasma glucose ≥200 mg/dL with classic hyperglycemia symptoms (polydipsia, polyuria) - no confirmation needed 3

Prediabetes Diagnosis Thresholds

• Fasting plasma glucose 100-125 mg/dL (impaired fasting glucose) 3
• 2-hour plasma glucose 140-199 mg/dL during 75-g OGTT (impaired glucose tolerance) 3
• HbA1c 5.7-6.4% 3

Test Selection

All three tests (fasting glucose, 2-hour OGTT, HbA1c) are equally appropriate for screening and diagnosis. 3, 1 Choose based on practical considerations:

• Fasting plasma glucose: Requires 8-hour fast; most cost-effective 2
• HbA1c: Most convenient (no fasting required); greater preanalytical stability 3
• 2-hour OGTT: Diagnoses more cases but requires 3 days of adequate carbohydrate intake (≥150 g/day) beforehand 3

Important Testing Caveats

Do not use HbA1c in these conditions (use plasma glucose only): 3

• Anemia or hemoglobinopathies 3
• Pregnancy (second/third trimesters) 3
• Hemodialysis 3
• Recent blood loss or transfusion 3
• Erythropoietin therapy 3

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Treatment Targets and Monitoring

Glycemic Targets

Target HbA1c <7% for most nonpregnant adults with type 2 diabetes. 4

More stringent target (HbA1c <6.5%) for patients with: 4

• Short diabetes duration 4
• Long life expectancy 4
• No existing complications 4
• No significant cardiovascular disease 4

Less stringent target (HbA1c <8%) for patients with: 4

• History of severe hypoglycemia 4
• Limited life expectancy 4
• Advanced microvascular or macrovascular complications 4
• Extensive comorbid conditions 4
• Long-standing diabetes difficult to control despite comprehensive treatment 4

HbA1c Monitoring Frequency

• Every 3 months when therapy has changed or glycemic targets not met 4
• Every 6 months once stable control achieved 4

Blood Glucose Monitoring

• Patients on insulin or medications with hypoglycemia risk: perform finger-stick blood glucose monitoring 4
• Patients on multiple daily insulin injections or pump therapy: test ≥3 times daily 4
• Consider continuous glucose monitoring (CGM) for: unexplained severe/recurrent hypoglycemia, hypoglycemia unawareness, nocturnal hypoglycemia, large glucose excursions, or refractory hyperglycemia 4

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Pharmacologic Management

First-Line Therapy

Metformin is first-line therapy for most patients with type 2 diabetes. 5

For patients with cardiovascular disease, kidney disease, or high cardiovascular risk: initiate glucagon-like peptide-1 receptor agonist (GLP-1RA) or sodium-glucose cotransporter 2 inhibitor (SGLT2i) early, in addition to metformin. 5

These medications provide:

• 12-26% reduction in atherosclerotic cardiovascular disease 5
• 18-25% reduction in heart failure 5
• 24-39% reduction in kidney disease progression 5

Add-On Medications

Common second-line agents include: 5

• Dual GIP/GLP-1 receptor agonists (weight loss >10% in many patients) 5
• Dipeptidyl peptidase-4 inhibitors 5
• Sulfonylureas 5
• Thiazolidinediones 5

Approximately one-third of patients require insulin during their lifetime. 5

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Cardiovascular Risk Management

Blood Pressure Targets

Screen blood pressure at every diabetes visit. 2

Target systolic blood pressure <130 mmHg and diastolic <80 mmHg for most patients. 2

• Patients with systolic 130-139 or diastolic 80-89 mmHg: lifestyle therapy for maximum 3 months, then add pharmacologic therapy if targets not achieved 2
• Patients with systolic ≥140 or diastolic ≥90 mmHg: immediate pharmacologic therapy plus lifestyle modification 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 indications: 2

• All diabetic patients with overt cardiovascular disease 2
• Diabetic patients >40 years with one or more cardiovascular risk factors 2
• Consider for patients <40 years if LDL >100 mg/dL or multiple risk factors 2

LDL cholesterol targets: 2

• Primary goal: LDL <100 mg/dL for patients without overt cardiovascular disease 2
• Optional goal: LDL <70 mg/dL for patients with overt cardiovascular disease using high-dose statin 2
• If targets not reached on maximal statin: aim for 30-40% LDL reduction from baseline 2

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Lifestyle Modification

Weight Management and Physical Activity

Intensive lifestyle modification (calorie restriction, ≥150 minutes/week physical activity, self-monitoring, motivational support) decreases diabetes incidence by 6.2 cases per 100 person-years over 3 years in prediabetes. 6

Physical activity reduces HbA1c by 0.4-1.0% and improves cardiovascular risk factors. 5

Dietary Recommendations

• Reduce saturated fat, trans fat, and cholesterol intake 2
• Increase omega-3 fatty acids, viscous fiber, and plant stanols/sterols 2
• DASH-style dietary pattern for hypertension management 2
• Reduce sodium and increase potassium intake 2
• No specific diet proven most effective for type 2 diabetes outcomes 5

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Prediabetes Management

For prediabetes, intensive lifestyle modification is first-line therapy, with metformin as an alternative. 6

Metformin is most effective for: 6

• Women with prior gestational diabetes 6
• Individuals <60 years with BMI ≥35 6
• Fasting plasma glucose ≥110 mg/dL 6
• HbA1c ≥6.0% 6

Metformin decreases diabetes risk by 3.2 cases per 100 person-years over 3 years. 6

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Immunizations

• Annual influenza vaccine for all diabetic patients ≥6 months of age 2
• Pneumococcal polysaccharide vaccine for all diabetic patients ≥2 years of age (revaccinate once if >64 years and prior vaccine >5 years ago) 2
• Hepatitis B vaccination per CDC recommendations 2

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Long-Term Benefits of Intensive Glucose Control

Intensive glucose-lowering strategies (HbA1c <7%) reduce microvascular disease by 3.5%, myocardial infarction by 3.3-6.2%, and mortality by 2.7-4.9% over 20 years compared to conventional treatment. 5 These benefits take years to manifest, emphasizing the importance of early diagnosis and sustained glycemic control. 5