What Is a Cortisol Blood Test?

Cortisol is the primary stress hormone. It follows a circadian rhythm.

Normal (8 AM)

• 6–23 µg/dL
• Afternoon is roughly half

High Cortisol

• Cushing's syndrome
• Chronic stress
• Oral steroids
• Obesity

Low Cortisol

• Addison's disease
• Pituitary insufficiency
• Steroid withdrawal

Alternative Tests

• 24-hour urine free cortisol
• Midnight salivary cortisol
• Dexamethasone suppression test