Understanding the marker
Cortisol helps regulate the body's use of energy and response to illness. A blood test can help assess specific hormone questions; it does not measure everyday stress or exhaustion.
Cortisol changes through the day, so the actual collection time and planned test method are essential. Sleep, illness and medicines can affect it. Follow the individual collection instructions; a randomly timed blood result is not sufficient to diagnose cortisol excess or deficiency.
What does high Cortisol (serum) mean?
A high cortisol result can have several explanations. Timing, sleep, illness and medicines help interpret it. It does not establish chronic stress or a hormone disorder on its own; specific follow-up tests may be needed.
What does low Cortisol (serum) mean?
A low cortisol result must be interpreted against the collection time, medicines and symptoms. When it is unexpectedly low for that context, a clinician may need further tests to assess cortisol production.
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This is general information about the marker, not an assessment of your values and not medical advice. Last updated: October 2026.