Cortisol, fact-checked: hormone, disease, hype

"Cortisol belly", "cortisol face", "cortisol detox": on social media, the stress hormone has become the universal culprit – for belly fat, a round face and exhaustion. An analysis of highly engaged TikTok videos, presented at a British endocrinology conference in March 2026, found "widespread misinformation and oversimplification": cortisol was cast as the root cause of belly fat and fatigue often to promote unproven supplements. Time to separate physiology and real disease from marketing.

What cortisol does

Cortisol is made in the adrenal glands under control of the hypothalamus and pituitary. It maintains blood sugar, helps regulate salt balance and blood pressure, and damps inflammation, which is why synthetic glucocorticoids ("steroids") are used as anti-inflammatory drugs. Under acute stress it rises to mobilise energy.

Cortisol follows a daily rhythm: it peaks around the time of waking and falls to its lowest point at night. So a single value says little: it depends on the time of day, on acute stress (illness, surgery, pain) and on the sample – blood, saliva, urine and hair measure different things. Depression, alcohol dependence, poorly controlled diabetes and severe obesity can also raise cortisol mildly without any adrenal disease.

"Cortisol belly" and "cortisol face": the kernel of truth

In Cushing's syndrome, cortisol is persistently too high. Typical features are fat gain on the abdomen, neck and face with thin arms and legs, muscle and bone loss, diabetes and high blood pressure. The most common cause is steroid medication. Endogenous Cushing's – usually from a pituitary or adrenal tumour – is rare: European studies found two to three new cases per million people per year.

Chronic stress and weight are linked, too. In the English Longitudinal Study of Ageing, 2,527 people aged 54 to 87 with higher hair cortisol had, on average, a higher BMI, a larger waist and more persistent obesity. Whether cortisol is cause or consequence, the authors note, is unknown.

… and what is not true

"Cortisol face" is not a medical term. A round face or belly fat alone does not point to excess cortisol; the Endocrine Society guideline lists facial fullness and obesity among the poorly discriminating signs. More telling are easy bruising, facial plethora (a ruddy face), weakness of the hip and shoulder muscles, and reddish-purple stretch marks wider than 1 cm.

As for the "cortisol cocktail" of orange juice, coconut water and sea salt, a Cleveland Clinic endocrinologist sees no evidence that it lowers cortisol or improves adrenal function. "Cortisol detox" programmes rest on testimonials, not controlled trials.

"Adrenal fatigue": a diagnosis without a disease

The idea is that chronic stress exhausts the adrenals. A systematic review by Cadegiani and Kater (2016) examined 58 studies; in 16 of 26 studies the daily salivary cortisol pattern did not differ between fatigued people and controls. The authors concluded there is no substantiation that "adrenal fatigue" is an actual medical condition. The Endocrine Society likewise finds no scientific proof.

The term persists because the exhaustion is real and the concept offers a simple, treatable explanation. The danger lies in treatment: taking hydrocortisone or adrenal hormones without need can suppress your own cortisol production; after stopping, the adrenals can stay "asleep" for months, with a risk of life-threatening adrenal crisis. And the real cause – depression or sleep apnoea, for example – goes unrecognised.

Cortisol tests sold online

Saliva reflects cortisol at the moment of sampling, 24-hour urine the day's output, and hair an average over weeks (2 cm corresponds to about two months). A saliva test can be medically useful – as a late-night value, measured twice, when Cushing's is suspected, because loss of the night-time low is a consistent finding there. Multi-sample "stress profiles" answer no such question, and hair cortisol is not among the guideline-recommended tests. The Endocrine Society explicitly recommends against widespread testing outside defined groups. For healthy people the result has no clinical consequence – except the risk of a false alarm that ends in buying supplements. In Germany they may be sold as IGeL, self-pay services outside statutory insurance (see our IGeL article).

Supplements marketed to lower cortisol

Ashwagandha is the best known. A 2022 meta-analysis (12 trials, 1,002 participants) found lower scores on stress and anxiety questionnaires but rated the certainty of evidence as low. A 2024 meta-analysis (9 trials, 558 participants) found slightly lower serum cortisol, with a confidence interval reaching almost to zero. Trials are small and short. Against this stands a safety signal: case series describe liver injury with jaundice, and in an Indian series of 23 patients, three people with pre-existing liver disease died of liver failure. Germany's Federal Institute for Risk Assessment (BfR) has advised against ashwagandha products since September 2024, especially for children, pregnant or breastfeeding women and people with liver disease, stating that no safe intake level can be derived. Denmark reportedly banned ashwagandha in food supplements in 2023.

Phosphatidylserine: in a manufacturer-funded trial of 75 healthy men, it did not change the cortisol response to a laboratory stress test overall; an effect appeared only in a subgroup. Magnesium: a review of 18 studies found hints of less anxiety, but study quality was poor. More in our article on supplements.

When cortisol testing is indicated

For an adrenal incidentaloma, the European Society of Endocrinology (2023 guideline) recommends the 1 mg dexamethasone test for everyone – see incidental findings in liver, kidney and adrenal.

What actually helps with chronic stress

The goal is less strain, not an "optimised" lab value. A JAMA Internal Medicine meta-analysis of 47 randomised trials found small to moderate improvements in anxiety and depression with mindfulness programmes; evidence for stress itself was low. The Endocrine Society recommends exercise, a healthy diet and regular sleep; see our articles on stress and cortisol, sleep and loneliness.

What this means for you

• Signs of too much cortisol: wide purple stretch marks; easy bruising; difficulty climbing stairs or rising from a squat; new high blood pressure or diabetes, especially at a younger age.
• Signs of too little cortisol: fatigue with loss of appetite and weight; dizziness on standing; salt craving; darkening of the skin. Rapid worsening is an emergency.
• Ask: What suspicion is being tested, with which test, at what time of day? What follows from the result?

This article is general information and not individual medical advice. Decisions about tests and treatment belong in a conversation with your own physician.