wie kann man cortisol messen — which blood markers matter?

Cortisol is commonly measured in blood, saliva, urine, or hair. For blood markers, the key parameters are: serum cortisol (morning fasting, due to circadian rhythm), possibly a dexamethasone suppression test for functional assessment, and ACTH (adrenocorticotropic hormone) to differentiate primary from secondary adrenal insufficiency. 24-hour urinary free cortisol reflects total production. However, single blood values are often unreliable because cortisol fluctuates with stress, time of day, and diet. If adrenal disorders or Cushing's syndrome are suspected, an endocrinological workup is essential. Direct-to-consumer tests (e.g., saliva-based) can give rough indications but do not replace medical diagnosis. The evidence for clinical use is strong (guidelines), but for consumers without medical interpretation, the utility is limited.