wie kann ich cortisol messen — which blood markers matter?

Cortisol is typically measured in blood (serum/plasma), saliva, or 24-hour urine. Key blood markers include: 1) morning cortisol (around 6–9 AM) – reflects basal adrenal function; 2) evening cortisol (around 10–11 PM) – assesses circadian rhythm; 3) ACTH – helps differentiate primary (adrenal) from secondary (pituitary) causes of cortisol dysregulation. A dexamethasone suppression test can further evaluate overproduction. Free cortisol in 24-hour urine is also a well-established marker. Important: single measurements are often unreliable because cortisol is secreted in pulses and fluctuates with stress. Home tests (e.g., salivary cortisol day profiles) have limited validity – they can indicate trends but cannot replace clinical diagnosis. Evidence for clinical cortisol testing is strong (human-strong), but weaker for consumer kits. Caveat: reference ranges vary by lab, time of day, and method. If adrenal insufficiency or Cushing's syndrome is suspected, consult an endocrinologist.