How is insulin resistance checked and managed?

Diagnosing and Managing Insulin Resistance

Insulin resistance should be assessed using fasting plasma insulin levels, with normal <15 mU/L, borderline high 15-20 mU/L, and high >20 mU/L, or by calculating HOMA-IR with values >4.65 indicating insulin resistance. 1, 2

Risk Assessment for Insulin Resistance

• Overweight or obesity (BMI ≥25 kg/m² or ≥23 kg/m² in Asian Americans) is a major risk factor for insulin resistance 1
• Family history of type 2 diabetes significantly increases risk of insulin resistance 1, 3
• Certain racial/ethnic groups have higher predisposition: American Indian, African American, Hispanic, or Asian/Pacific Islander 3, 1
• Physical signs of insulin resistance include acanthosis nigricans (dark, velvety skin patches), hypertension, dyslipidemia, and polycystic ovary syndrome 3, 1
• Children who are overweight with a family history of type 2 diabetes or from high-risk ethnic groups should be evaluated for insulin resistance 3

Diagnostic Tests for Insulin Resistance

Primary Diagnostic Methods:

• Fasting plasma glucose: Values between 100-125 mg/dL indicate impaired fasting glucose, suggesting insulin resistance 3, 1
• Fasting plasma insulin: Normal <15 mU/L, borderline high 15-20 mU/L, high >20 mU/L 3, 1
• HOMA-IR calculation: Values >4.65 indicate insulin resistance in adults 1, 2
• Oral glucose tolerance test (OGTT): 2-hour glucose values of 140-199 mg/dL indicate impaired glucose tolerance 3, 1
• Hemoglobin A1C: Values between 5.7-6.4% suggest prediabetes and potential insulin resistance 3, 1

Advanced Diagnostic Methods:

• Euglycemic insulin clamp: Gold standard for research purposes, not typically used in clinical practice 4, 5
• Intravenous glucose tolerance test: Another research method for precise measurement 4, 6

Clinical Decision Rules for Diagnosing Insulin Resistance

Diagnose insulin resistance if any of these conditions are met 2:

• BMI >28.9 kg/m²
• HOMA-IR >4.65 (corresponding to fasting insulin >20.7 μU/ml)
• BMI >27.5 kg/m² AND HOMA-IR >3.60 (corresponding to fasting insulin >16.3 μU/ml)

Management of Insulin Resistance

Non-Pharmacological Interventions:

• Weight loss to attain healthy body weight is the cornerstone of treatment 3, 7
• Physical activity: At least 30 minutes of moderate-intensity exercise daily 3, 7
• Dietary modifications: Increase fiber intake, reduce refined carbohydrates and saturated fats 3, 7
• For children and adolescents: Family-based interventions with parental role modeling of healthy habits 3

Pharmacological Management:

• Metformin may be considered for those with prediabetes or high risk of developing type 2 diabetes 8
• Metformin has been shown to improve insulin sensitivity and reduce fasting plasma glucose 8
• Pharmacotherapy is generally not recommended for isolated insulin resistance without other metabolic abnormalities 7

Monitoring and Follow-up

• Regular assessment of fasting glucose, insulin levels, and HbA1c to track progression 3, 1
• Screening for comorbidities: hypertension, dyslipidemia, and cardiovascular disease 3, 1
• In children at risk, repeat testing at minimum 3-year intervals or more frequently if BMI is increasing 3

Common Pitfalls and Considerations

• Insulin resistance testing should be performed in the fasting state to avoid postprandial variations 1
• Medications affecting glucose metabolism should be noted when interpreting results 1
• Stress hyperglycemia during acute illness can temporarily mimic insulin resistance 1
• The American Diabetes Association recommends fasting insulin measurement primarily for research purposes, not as a routine diagnostic test 9
• C-peptide measurement alongside insulin can help differentiate between endogenous insulin production and exogenous insulin administration 1, 10

Special Populations

• In pregnant women, fasting glucose concentrations are lower, but postprandial glucose and insulin levels are higher than in non-pregnant women 9
• For children and adolescents, BMI percentiles rather than absolute values should be used (overweight ≥85th percentile, obese ≥95th percentile) 3
• Asian populations may develop insulin resistance at lower BMI thresholds (≥23 kg/m²) 3, 1