Cortisol Blood Test

Measures morning serum cortisol — the primary stress hormone produced by the adrenal glands. Cortisol follows a strong circadian rhythm, peaking within 30 minutes of waking and declining through the day. Chronically elevated cortisol drives weight gain (particularly visceral fat), disrupts sleep architecture, suppresses immune function, and accelerates muscle loss. Chronically low cortisol suggests adrenal insufficiency or HPA axis exhaustion from prolonged stress.

Cortisol is the body's primary stress hormone, produced by the adrenal glands in a strong circadian pattern — peaking within 30 minutes of waking and declining through the day to reach its lowest point around midnight. This rhythm governs energy, alertness, immune function, and metabolism. Disruptions to cortisol regulation affect virtually every system in the body. Chronically elevated cortisol drives visceral fat accumulation (particularly around the midsection), breaks down muscle tissue, suppresses immune function, impairs sleep architecture, raises blood sugar, and accelerates bone loss. It is a key mediator of the damage caused by chronic psychological stress, shift work, and sleep deprivation. Conversely, chronically low cortisol — sometimes called adrenal insufficiency or HPA axis dysfunction — causes profound fatigue, lightheadedness on standing, salt cravings, and an inability to mount an appropriate stress response. This test measures morning serum cortisol, which must be collected before 10am for clinical accuracy. A morning blood draw captures the cortisol awakening response — the time when levels should be at their highest. A result that falls below the expected morning range suggests adrenal underfunction, while an unusually elevated result may indicate chronic stress, Cushing's syndrome, or exogenous glucocorticoid exposure. Results are available within 2-3 business days through ClearLabs' secure digital dashboard. For a more comprehensive assessment of cortisol patterns throughout the day, ClearLabs also offers the DUTCH Hormone Panel, which captures cortisol metabolites and daily rhythm rather than a single time point.