Endocrine & Metabolic

An A1c of 6.5% or higher meets the diagnostic threshold. In the absence of unequivocal hyperglycemia, a second confirmatory test (repeat A1c, FPG, or OGTT) is needed.

A fasting plasma glucose of 126 mg/dL or higher (fasting at least 8 hours) is diagnostic. Impaired fasting glucose (prediabetes) is 100-125 mg/dL.

A 2-hour plasma glucose of 200 mg/dL or higher during a 75-g OGTT, or a random glucose of 200 mg/dL or higher PLUS classic hyperglycemic symptoms, diagnoses diabetes.

Screen all adults beginning at age 35, and at any age if overweight/obese (BMI ≥25, or ≥23 in Asian Americans) with one or more risk factors. Rescreen at least every 3 years if normal.

Type 1: younger/leaner, abrupt onset, prone to DKA, low/absent C-peptide, positive autoantibodies (GAD-65, IA-2, ZnT8). Type 2: older, overweight, insulin resistance, gradual onset, often metabolic syndrome features.

Metformin remains first-line for most patients alongside lifestyle modification, due to efficacy, low hypoglycemia risk, weight neutrality, and low cost. Start with lifestyle plus metformin unless contraindicated.