Is Cortisol useful for stress?

Cortisol is essential for the acute stress response: it mobilizes glucose, suppresses non-essential functions, and modulates inflammation. In short bursts, it is clearly useful. However, chronic elevation—common in modern lifestyles—is linked to visceral fat accumulation, insulin resistance, hypertension, impaired immunity, and cognitive decline. The provided context does not directly discuss cortisol; this answer is based on well-established human physiology (evidence: human-strong). Consumer tests for cortisol (saliva, hair, blood) can indicate long-term stress patterns but are not diagnostic for disorders like Cushing's or adrenal insufficiency. Their utility is limited by high intra-individual variability and lack of standardized reference ranges for 'optimal' levels. For stress management, evidence supports lifestyle interventions (sleep, exercise, mindfulness) over repeated cortisol testing. A single measurement is rarely actionable; trends over time with clinical correlation are more meaningful.