Cortisol is the main stress hormone, produced by the adrenal glands. It mobilizes the body: it raises blood glucose, lifts blood pressure, and suppresses inflammation and immunity.
The key thing to understand: cortisol is not a "bad" hormone — without it you could not wake up or cope with a load. The problem is created not by cortisol itself but by its chronically elevated level, at which a useful short-term response turns into a constant destructive background.
Reference ranges
Cortisol has a pronounced daily rhythm — the normal range depends on the time of the draw:
| Morning (8:00), blood | 170 – 540 nmol/L |
| Evening (after 17:00), blood | 60 – 330 nmol/L |
| The main sign of normality | the morning level is noticeably higher than the evening |
| Saliva, late evening | low (used to screen for hypercortisolism) |
What an elevated level means
Chronically high cortisol is a typical consequence of prolonged stress and lack of sleep. It raises glucose, intensifies insulin resistance, redistributes fat to the belly, breaks down muscle and reduces bone density.
Signs: abdominal obesity with thin limbs, sugar cravings, insomnia (especially waking at 3–4 a.m.), anxiety, high blood pressure, frequent infections, poor wound healing.
The extreme is Cushing's syndrome (a tumor or long-term glucocorticoid use): purple stretch marks, a "moon" face, marked muscle weakness. This already requires an endocrinologist.
What a low level means
Persistently low cortisol is a dangerous state that requires a doctor. It is adrenal insufficiency (Addison's disease) or a consequence of abruptly stopping long-term glucocorticoid therapy.
Symptoms: marked weakness, weight loss, low blood pressure and dizziness on standing, salt craving, skin darkening, nausea.
Separately: "adrenal fatigue" is not a diagnosis recognized by medicine. It is a popular but unconfirmed concept; the symptoms attributed to it are usually explained by lack of sleep, depression, anemia or hypothyroidism.
How the test is done
Blood is drawn in the morning, between 8:00 and 9:00, in a calm state, fasting. The day before, avoid alcohol and intense workouts, and try to get enough sleep.
For assessing chronic stress a single blood test is poorly suited. More informative is salivary cortisol at several points across the day (to assess the daily rhythm) or cortisol in 24-hour urine. If hypercortisolism is suspected, a doctor orders suppression tests.
What affects the value
- Chronic stress — the main factor in prolonged elevation.
- Lack of sleep and shift work — break the cortisol daily rhythm.
- Alcohol and excess caffeine — raise the level.
- Overtraining — excess load without recovery raises cortisol.
- Glucocorticoids (including creams and inhalers) — suppress the body's own production.
- Regular sleep, breathing practices and moderate activity — lower it.
Related calculators
Cortisol does not go directly into the calculation, but it intensifies insulin resistance and metabolic risk — these tools show its consequences:
Frequently asked questions
How do I know if my cortisol is high?
A single blood test shows little: the prick itself raises cortisol. More informative is assessing the daily rhythm — salivary cortisol at several points across the day. Indirect signs of chronic elevation: belly fat with thin arms and legs, waking at 3–4 a.m., sugar cravings, anxiety.
Does "adrenal fatigue" exist?
As a medical diagnosis — no, it is not recognized. It is a popular concept unsupported by research. The symptoms attributed to it (fatigue, feeling run down) are almost always explained by other causes: lack of sleep, depression, iron deficiency or hypothyroidism. Those are what should be checked.
How do you lower cortisol?
The main thing is to restore sleep (the most powerful lever), remove chronic stress, limit alcohol and caffeine, and avoid overtraining. Moderate regular activity lowers cortisol, whereas exhausting workouts without recovery raise it.