Free Insulin

Endocrinology

Normal Reference Ranges

Adult

2.6 - 24.9 µIU/mL

Pediatric

2.0 - 20.0 µIU/mL

Clinical Significance

Assesses pancreatic beta-cell function and insulin sensitivity. Elevated in insulin-resistance states and pathologically high in insulinoma during fasting hypoglycemia.

Causes of High

  • Insulin resistance (Type 2 Diabetes, Metabolic Syndrome)
  • Insulinoma
  • Exogenous insulin administration
  • Cushing syndrome

Causes of Low

  • Type 1 Diabetes mellitus
  • Beta-cell exhaustion in long-standing Type 2 Diabetes
  • Hypopituitarism