High cortisol: what it means and what to do

A high cortisol in a blood test usually does not mean a disease. It is often down to the time of the test, the pill, an illness or a night without sleep. Cushing’s syndrome is rare, and it is looked for with different tests that your doctor chooses.

What high cortisol means

Cortisol is the hormone your body uses to respond to strain. It rises every morning when you wake and rises when you are ill, in pain or short of sleep. A result above the limit on your report is not enough for a diagnosis on its own.

To find out whether there is a real excess, doctors use other tests: saliva cortisol at 11 at night, 24-hour urine (usually two collections) or a morning blood test after a dexamethasone tablet taken the night before. After dexamethasone, a result above 1.8 µg/dL is not normal.

If the tests confirm an excess, the next step is finding where it comes from: the pituitary, an adrenal gland or, more rarely, another organ. That is why ACTH is measured too.

What causes high cortisol

The common causes come first. Cushing’s is last because it is rare.

• The time and the way of the test: Cortisol peaks when you wake. A stressful wait or a difficult blood draw also raise it a little.
• The pill, oestrogen treatment, pregnancy: They raise the protein that carries cortisol: the total goes up even when free cortisol is normal.
• An illness, pain or surgery: Your body makes more cortisol to deal with them. The test is repeated when you are well.
• Depression, alcohol, severe obesity, poorly controlled diabetes: They can raise it for months without Cushing’s. Your doctor takes them into account.
• Very hard training or too little food: Extreme physical strain and undernutrition raise cortisol.
• Cushing’s syndrome: It is rare. It can start from a small benign tumour of the pituitary or an adrenal gland. The most common cause of Cushing’s, though, is steroid medicines taken for a long time.

Symptoms of high cortisol

A high cortisol for a few days causes no symptoms. An excess that lasts months, as in Cushing’s, can cause:

• Weight gain on the tummy, face and neck, with thin arms and legs
• Wide reddish purple stretch marks on the tummy and sides
• Easy bruising and thin skin
• Weak thighs: struggling to get up from a chair
• High blood pressure and high blood sugar, sometimes together

Several of these signs together are a reason to see your doctor. Just one, like a few extra kilos on the tummy, usually has other causes.

High cortisol and stress

You often read that stress raises cortisol and makes you gain weight. Sudden stress raises cortisol briefly: that is its job. Everyday stress, though, does not usually push blood cortisol out of the normal range.

A normal cortisol does not mean stress is not weighing on you. And feeling better is not about lowering a number: sleep, movement and the right support matter.

Which tests to read alongside it

These tests help show whether the excess is real and where it comes from.

What to do if your cortisol is high

Where to start:

• Check the time of the test, and whether you were ill, short of sleep, or taking the pill or steroids around then.
• Take the report to your doctor. Without signs of Cushing’s, repeating the test is often enough, or nothing more is needed.
• If your doctor suspects a real excess, they order the right tests: late-evening saliva, 24-hour urine or the dexamethasone test.
• Do not take supplements to lower cortisol: they do not treat a cause and can confuse the tests. Ask your doctor.

If you take steroid medicines, do not stop them on your own: after long use they must be tapered with your doctor.

High cortisol: when to worry

Talk to your doctor if:

• Your cortisol is above the limit on your report and you have several signs together: a rounder tummy and face, reddish purple stretch marks, bruising, weak thighs.
• High blood pressure and high blood sugar have appeared together, especially if you are young.
• A lump on an adrenal gland was found by chance.
• You have a sudden, very severe headache, chest pain or sudden weakness in an arm or leg: call 112 or go to the emergency department.

Frequently asked questions

What are the symptoms of high cortisol? A rise for a few days causes none. An excess lasting months can cause weight on the tummy and face, reddish purple stretch marks, easy bruising, weak thighs, and high blood pressure and blood sugar.

How do I lower my cortisol? If the high result comes from the time of day, the pill or an illness, there is nothing to lower. If there is a real excess, the cause is treated with your doctor. Regular sleep and movement help with stress, not with correcting a lab report.

Does high cortisol make you gain weight? An excess lasting months, as in Cushing’s, causes weight gain on the tummy and face. Everyday stress does not usually raise cortisol enough to do that.

When should I worry about high cortisol? When it is high and several signs of Cushing’s show up together. A high result without symptoms is often down to the time of day or the pill: your doctor decides whether to repeat it.

Does the pill raise cortisol? Yes, total cortisol. Oestrogen raises the protein that carries it, so the number goes up without a real excess. Tell your doctor before the test.

Does Rosa test cortisol? No. Rosa measures blood sugar, HbA1c and potassium, which change with a real cortisol excess. If your doctor wants cortisol, they order it separately.

Sources

• Bornstein and colleagues, diagnosis and treatment of primary adrenal insufficiency: an Endocrine Society clinical practice guideline. Journal of Clinical Endocrinology and Metabolism, 2016. PMID 26760044
• Nieman and colleagues, the diagnosis of Cushing’s syndrome: an Endocrine Society clinical practice guideline. Journal of Clinical Endocrinology and Metabolism, 2008. PMID 18334580
• Cadegiani and Kater, adrenal fatigue does not exist: a systematic review. BMC Endocrine Disorders, 2016. PMID 27557747
• Fondazione Policlinico Universitario A. Gemelli IRCCS, clinical chemistry laboratory: list of tests and reference intervals, 2024. Policlinico Gemelli, elenco prestazioni CDS.002