Endocrine System

HbA1c >=6.5%, fasting plasma glucose >=126 mg/dL, 2-hour OGTT glucose >=200 mg/dL, or a random glucose >=200 mg/dL with classic hyperglycemic symptoms. In the absence of unequivocal hyperglycemia, a result should be confirmed by repeat testing.

Prediabetes is an HbA1c of 5.7-6.4%, an impaired fasting glucose of 100-125 mg/dL, or a 2-hour OGTT of 140-199 mg/dL (impaired glucose tolerance). It identifies patients at high risk who benefit from lifestyle intervention and sometimes metformin.

Type 1 is autoimmune destruction of pancreatic beta cells causing absolute insulin deficiency, typically younger lean patients prone to DKA, often with positive GAD-65/islet antibodies and low C-peptide. Type 2 is insulin resistance with relative deficiency, typically older overweight patients with metabolic syndrome and preserved or high C-peptide.

Metformin, a biguanide, is first-line. It decreases hepatic gluconeogenesis and improves peripheral insulin sensitivity without causing hypoglycemia or weight gain. Main risks are GI upset and rare lactic acidosis; it is held when eGFR <30 and around iodinated contrast.

SGLT2 inhibitors (e.g., empagliflozin) reduce heart failure hospitalization and slow CKD progression; GLP-1 receptor agonists (e.g., semaglutide) reduce atherosclerotic cardiovascular events and promote weight loss. Both are preferred add-ons in patients with established ASCVD, heart failure, or diabetic kidney disease.

An HbA1c <7% is reasonable for most nonpregnant adults. Stricter (<6.5%) may suit younger patients with short disease duration and no significant comorbidity; looser (<8%) suits the elderly or those with limited life expectancy, severe hypoglycemia history, or extensive comorbidity.