What Is Cortisol? How the Stress Hormone Works and Why Levels Matter (November 2026)

Medical information checked: November 4, 2026, 5:31 PM UTC.

Cortisol is a hormone your body needs every day. Made by the adrenal glands above your kidneys, it helps regulate blood sugar, blood pressure, metabolism, inflammation, and your response to physical or emotional stress. Although it is often called the “stress hormone,” cortisol is not inherently harmful. The important questions are whether your body is making an appropriate amount and whether its daily rhythm is working as expected.

Most short-term rises in cortisol are normal, including those associated with waking up, exercise, illness, or a demanding situation. Persistently abnormal levels can sometimes point to a medical condition, but symptoms such as fatigue, poor sleep, or changes in weight do not prove that cortisol is the cause. An appropriate diagnosis requires clinical assessment and, when indicated, targeted testing.

Destaques

• Cortisol is essential for energy regulation, blood pressure, immune activity, and responding to stress.
• Levels usually rise around waking and decline toward the night, so the timing of a test matters.
• Long-term cortisol excess can occur in Cushing’s syndrome; too little cortisol can occur with adrenal insufficiency.
• Sleep, movement, and stress-management habits support well-being, but they do not replace medical treatment for a hormone disorder.

What does cortisol do in your body?

Cortisol is a glucocorticoid steroid hormone produced by the adrenal cortex. It acts on many tissues rather than serving a single purpose. Its main jobs include helping the body make energy available by influencing glucose metabolism, maintaining the circulatory system’s response to changing demands, and limiting excessive inflammatory activity.

During a stressful event, cortisol works alongside other signals, including adrenaline, to help you respond. This is useful when you are facing an immediate challenge. Cortisol also supports ordinary functions when nothing stressful is happening. That is why a goal of “zero cortisol” is neither realistic nor healthy.

Australia’s healthdirect guide to cortisol describes its roles in stress response, glucose metabolism, blood pressure, and inflammation.

How is cortisol produced, and why is it higher in the morning?

Cortisol production is coordinated by a communication network called the hypothalamic-pituitary-adrenal (HPA) axis. The hypothalamus in the brain releases corticotropin-releasing hormone (CRH), the pituitary gland releases adrenocorticotropic hormone (ACTH), and ACTH signals the adrenal glands to make cortisol. Feedback from cortisol helps regulate further production.

For people who sleep at night and are awake during the day, cortisol generally increases around the time they wake and gradually falls toward bedtime. Sleep schedules, shift work, illness, stress, and medications can influence this pattern. One reading therefore cannot be interpreted sensibly without knowing when the sample was collected and why the test was ordered.

What causes high cortisol levels?

A temporary increase does not necessarily mean that something is wrong. Cortisol can rise with exercise, pain, acute illness, and psychological stress. The clinically important concern is sustained or inappropriate exposure to excess cortisol, especially when it is accompanied by a recognizable pattern of symptoms.

What are the signs of Cushing’s syndrome?

Cushing’s syndrome is a comparatively uncommon condition caused by prolonged exposure to too much cortisol. It may be associated with long-term use of high-dose glucocorticoid medications or, less commonly, tumors that increase cortisol production. Possible features include:

• Increasing weight around the abdomen and upper back, sometimes with a rounder face.
• Skin that bruises easily, broad stretch marks, or wounds that heal slowly.
• Weakness in the muscles of the upper arms or thighs.
• High blood pressure, elevated blood sugar, and mood changes.

These signs overlap with much more common health problems, so they should not be used for self-diagnosis. Healthdirect’s Cushing’s syndrome resource explains the symptoms, causes, and clinical assessment.

What happens when cortisol is too low?

Adrenal insufficiency occurs when the body cannot make enough cortisol for its needs. Addison’s disease is a type of primary adrenal insufficiency in which the adrenal glands are affected. Problems involving pituitary signaling can also cause inadequate cortisol production. Another important cause is suddenly stopping certain corticosteroid medicines after prolonged use.

Symptoms can develop gradually and include persistent tiredness, muscle weakness, loss of appetite, unintended weight loss, abdominal discomfort, and dizziness from low blood pressure. People with Addison’s disease may also develop darker patches of skin. These findings have many possible causes, but ongoing or worsening symptoms should be discussed with a clinician.

Emergency warning: An adrenal crisis can cause severe weakness, vomiting, abdominal pain, marked dizziness, fainting, or collapse. It requires immediate treatment. In Australia, call 000 for a suspected medical emergency. People already diagnosed with adrenal insufficiency should follow their prescribed emergency steroid plan while seeking urgent care. See healthdirect’s Addison’s disease and adrenal crisis advice.

How do doctors test cortisol levels?

There is no single cortisol test that answers every question. A general practitioner (GP) or endocrinologist chooses testing based on the symptoms, medical history, medications, and suspected condition. Common options include:

• Timed blood cortisol tests: Often collected in the morning when investigating low cortisol, with interpretation based on the sampling time and laboratory.
• Late-night salivary cortisol: May help assess whether cortisol falls appropriately late in the day when excess cortisol is suspected.
• 24-hour urine free cortisol: Measures cortisol excreted over a full day, sometimes used when investigating Cushing’s syndrome.
• Dexamethasone suppression test: Assesses whether cortisol production is appropriately reduced in response to a glucocorticoid medication.
• ACTH stimulation test: Checks how effectively the adrenal glands respond to a signal to release cortisol, particularly when adrenal insufficiency is suspected.

Lab results may be influenced by the time of sampling, illness, physical stress, and medications, including steroid treatment and some estrogen-containing medicines. A home wellness kit or a single isolated number cannot establish Cushing’s syndrome or adrenal insufficiency. The MedlinePlus cortisol test guide explains sampling and interpretation; the US National Institute of Diabetes and Digestive and Kidney Diseases describes diagnostic tests for Cushing’s syndrome and adrenal insufficiency.

Can you lower cortisol naturally?

If your concern is everyday stress rather than a diagnosed endocrine disorder, aim to improve overall health instead of chasing a particular cortisol number. Regular sleep and wake times, enjoyable physical activity, balanced meals, appropriate breaks, supportive relationships, and relaxation exercises can all help with stress management. Avoid using alcohol as a coping strategy, and consider whether late-day caffeine affects your sleep.

These habits are worthwhile, but claims that a supplement, “cortisol detox,” or one food can reliably treat a hormonal disorder are not supported by the diagnostic guidance above. Do not start or stop prescription corticosteroids, including prednisolone or hydrocortisone, without medical advice. Healthdirect’s stress-relief guidance offers practical relaxation, exercise, and sleep strategies.

When should you talk to a doctor about cortisol?

Consider booking an appointment with a GP if you have persistent unexplained fatigue, progressive muscle weakness, unusual bruising, a combination of weight and skin changes, recurrent low blood pressure or dizziness, or other symptoms that are interfering with daily life. This is especially important if you take, have recently reduced, or have stopped corticosteroid medicines.

A useful next step is to bring a list of medications (including inhalers, creams, injections, and supplements), a timeline of your symptoms, relevant health conditions, and any previous test results. Your clinician can determine whether cortisol testing is appropriate or whether another explanation is more likely. For nonemergency health advice in Australia, healthdirect can be reached on 1800 022 222.

FAQ: Common questions about cortisol

Is cortisol bad for you?

No. Cortisol is necessary for normal metabolism, blood pressure regulation, and the body’s response to stress. Problems can arise when levels are persistently too high or too low.

Does a cortisol belly mean I have high cortisol?

No. Abdominal weight gain alone cannot diagnose cortisol excess. Cushing’s syndrome is assessed using a pattern of clinical findings and appropriate medical tests, not body shape or social media claims.

What time of day should cortisol be tested?

It depends on the question the test is designed to answer. Some blood tests are collected in the morning, while tests for excess cortisol may use late-night saliva or 24-hour urine. Follow the collection instructions from your healthcare professional.

This article provides general health information and is not a substitute for personalized medical advice or emergency care.