Diabetes mellitus

A chronic metabolic disorder characterized by persistent hyperglycemia resulting from defects in insulin secretion, insulin action, or both, and clinically associated with polyuria, polydipsia, polyphagia, and long-term microvascular and macrovascular complications.

• HbA1c (average 3-month blood sugar):

  • Normal: <5.7% (<39 mmol/mol)

  • Prediabetes: 5.7% - 6.4% (39 - 47 mmol/mol)

  • Diabetes: ≥6.5% (≥48 mmol/mol)

• Fasting Plasma Glucose (FPG):

  • Normal: <100 mg/dL (<5.6 mmol/L)

  • Prediabetes: 100 - 125 mg/dL (5.6 - 6.9 mmol/L)

  • Diabetes: ≥126 mg/dL (≥7.0 mmol/L) on two separate tests

• Oral Glucose Tolerance Test (OGTT) / Random Glucose:

  • Diabetes: ≥200 mg/dL (≥ 11.1 mmol/L)

Causes

• Type 1 diabetes mellitus (autoimmune destruction of pancreatic β-cells)

• Type 2 diabetes mellitus (insulin resistance with progressive β-cell dysfunction)

• Gestational diabetes mellitus

• Genetic defects affecting insulin secretion or action

• Diseases of the exocrine pancreas

  • Chronic pancreatitis

  • Pancreatic cancer

  • Pancreatectomy

• Endocrine disorders causing insulin resistance or excess counter-regulatory hormones

  • Cushing syndrome

  • Acromegaly

  • Hyperthyroidism

  • Pheochromocytoma

• Medications

  • Glucocorticoids

  • Atypical antipsychotics

  • Thiazide diuretics

  • Calcineurin inhibitors

• Infections or systemic illness causing pancreatic injury or metabolic dysfunction

• Genetic syndromes associated with diabetes risk

  • Down syndrome

  • Turner syndrome

  • Klinefelter syndrome

• Pregnancy-related hormonal changes causing insulin resistance