Is cortisol good or bad? Why you need it

Cortisol isn’t a good hormone or a bad one. You need it to live. Trouble starts when the level is too high or too low for too long, or when the daily rise and fall is lost.

The “stress hormone” label makes cortisol sound like something to get rid of. This page explains why that is the wrong picture, and where cortisol really does cause problems.

What cortisol is for

The benefits are the ordinary jobs your body does every day. MedlinePlus and NIDDK say cortisol helps your body:

• respond to stress
• reduce inflammation
• control blood sugar and metabolism
• control blood pressure
• turn food into energy (NIDDK)

A 2017 review adds that the rise toward the end of the night frees up stored energy for the day ahead. See what cortisol does for the detail.

Why a spike isn’t a problem

Cortisol rises after exertion, illness or a scare. MedlinePlus lists stress, exercise, hot and cold temperatures and pregnancy among the everyday things that can change a cortisol result. A rise like this is the system doing its job. See how long cortisol stays in your system.

The daily rhythm also means that high values are expected at certain times. Cortisol peaks in the early morning and is lowest around midnight, so a value that is high at 8 a.m. can be ordinary, and a value that is low at midnight is normal too (Endocrine Reviews, 2024). See when cortisol is highest.

When too much cortisol becomes a problem

A short rise is fine. A long period of excess is not. NIDDK describes Cushing’s syndrome as a disorder in which the body makes too much cortisol over a long period, most often because of long-term, high-dose glucocorticoid medicine. Some tumors can also cause it. A 2024 review links glucocorticoid excess with raised blood pressure, high blood sugar, abnormal blood fats, weaker immunity and thinning bones.

Timing matters as well as the amount. NIDDK says that normally cortisol production drops just after we fall asleep, and that in Cushing’s syndrome the level doesn’t drop. A 2017 review describes chronic stress with cortisol staying high at the usual low point as the point where some of its beneficial actions turn harmful, and says evidence from animal and human studies links chronic exposure to modestly raised cortisol with memory deficits, weakened immune function and cardiometabolic and reproductive disturbances (Endocrine Reviews, 2017). That is the review’s own summary of the evidence, not a statement about any one person, and it doesn’t mean everyday stress will cause these problems.

If you are worried about high cortisol, see high cortisol. Tests for Cushing’s syndrome include late-night saliva, a 24-hour urine collection and a dexamethasone suppression test. A clinician arranges those, and a single blood cortisol can’t diagnose or rule out the condition.

When too little cortisol becomes a problem

Low cortisol is not a goal. NIDDK lists long-lasting fatigue, muscle weakness, loss of appetite, weight loss and abdominal pain as the most common symptoms of adrenal insufficiency, which includes Addison’s disease. MedlinePlus says that without treatment, cortisol levels that are too high or too low can be very serious.

Low cortisol also has a common medicine-related cause. NIDDK says the most common cause of adrenal insufficiency overall is suddenly stopping corticosteroids after taking them for a long time. If you take a steroid medicine, never stop it or change the dose on your own. Ask your prescriber.

Some signs need urgent care and not a test. NIDDK says that if you have adrenal insufficiency and symptoms of adrenal crisis, you need emergency medical treatment. It lists sudden, severe pain in the lower back, abdomen or legs, vomiting and diarrhea, weakness, confusion and loss of consciousness. It also says a severe infection, or severe diarrhea or vomiting that stops you keeping steroid pills down, needs immediate medical attention. If you have adrenal insufficiency or take a steroid medicine and have any of these, call 911 or go to an emergency room. Don’t wait for a test or an appointment. If you aren’t sure how serious your symptoms are, get urgent care rather than wait.

For the condition itself, see low cortisol.

Is cortisol a real thing?

Yes. Cortisol is a hormone with a measurable level in blood, urine and saliva. MedlinePlus describes tests that measure it and the conditions they help diagnose.

What isn’t well supported is the idea that vague tiredness or stress is caused by “cortisol imbalance” or “adrenal fatigue”. A 2024 paper in the Journal of the Endocrine Society says adrenal fatigue has never been scientifically proven to exist, and that the saliva cortisol profiles sold for it have never been validated (J Endocr Soc, 2024). The same paper says the accepted tests, cortisol, ACTH and the ACTH stimulation test, are usually normal in people given the label. See adrenal fatigue.

Questions people ask

Is high cortisol good or bad?

It depends on when and for how long. High in the early morning is normal. A brief rise with stress or exercise is normal. A long stretch of excess, or a level that stays high when it should fall at night, can point to a medical condition and is worth discussing with a clinician.

Is low cortisol good or bad?

Low late in the evening and at night is normal. Low cortisol that persists is not a goal. It can be a sign of adrenal insufficiency, which is a real condition with a defined work-up, or it can be an effect of stopping steroid medicine. A result under a lab’s range isn’t a diagnosis by itself.

What is cortisol used for?

Cortisol is used by the body to manage stress responses, energy, inflammation and blood pressure. Cortisol is also the name of a lab test, which MedlinePlus says is used to help diagnose or rule out conditions that cause too much or too little cortisol. Cortisol-like medicines are used for other conditions, and they belong with a prescriber.

Can I lower or raise my cortisol myself?

This page doesn’t cover that. Cortisol sits inside a tightly controlled feedback system, and the useful question is why a level is high or low, which needs a clinician. If you take a steroid medicine, don’t change it without your prescriber.

Keep reading

• What is cortisol?

  The overview: where it comes from and why levels change.

• What cortisol does

  The jobs it does, system by system.

• High cortisol

  What too much can mean and how it is worked up.

• Low cortisol

  What too little can mean, including the emergency signs.