Cortisol, stress and women's health
What the stress hormone cortisol does, how it changes through the day, what high or low levels can mean, and where the cortisol hype misleads.
Reviewed by Emma Carter, Senior Health & Nutrition Editor
Cortisol has become the internet's favorite villain, blamed for belly fat, tiredness and almost everything else, with a supplement to match each claim. The real hormone is more interesting and less sinister. Cortisol is essential, it follows a daily rhythm, and true problems with it are specific medical conditions rather than the vague "high cortisol" of marketing.
What cortisol does
Cortisol is your main stress hormone, produced by the adrenal glands that sit on top of your kidneys. Its reputation as the stress hormone is fair but incomplete, because it does far more than handle stress:
- Responds to stress, including illness, injury and surgery
- Regulates metabolism and how your body uses fuel
- Controls blood sugar and manages blood pressure
- Calms inflammation
- Helps run your sleep-wake cycle
Because it reaches nearly every tissue, cortisol is something your body carefully controls rather than a toxin to be eliminated.
The daily rhythm
Cortisol is not meant to be flat. It follows a clear daily curve: highest in the early morning, which helps you wake and get going, then declining through the day to its lowest point around midnight. This rhythm is normal and healthy.
That pattern is why testing has to be timed. A single number means little without knowing when it was taken, and a "high" morning reading may be completely normal. Disrupted sleep and shift work blunt the rhythm, which is one reason poor sleep and stress feed into each other.
When cortisol is genuinely too high or low
Real cortisol disorders exist, and they are distinct from everyday stress.
| Condition | What it looks like | Notes |
|---|---|---|
| Too high (Cushing's syndrome) | Central weight gain, rounded face, thin easily-bruised skin, muscle weakness, high blood pressure, irregular periods | Uncommon; often from long-term steroid medication or, rarely, a tumor |
| Too low (Addison's, adrenal insufficiency) | Fatigue, weight loss, low blood pressure, salt cravings, skin darkening | Serious and needs treatment |
The point worth holding onto: ordinary stress does not raise cortisol to disease levels, and these conditions are diagnosed with proper testing, not guessed from symptoms.
The "cortisol" hype
Much of what you read about lowering cortisol is oversold. Chronic stress can affect health through many pathways, but the idea that a supplement will meaningfully "reset" your cortisol and melt away weight gain is not supported by good evidence. The related idea of "adrenal fatigue," where everyday stress supposedly exhausts the adrenal glands, has been examined directly: a systematic review of 58 studies found no proof it exists and no endocrine society recognizes it (BMC Endocrine Disorders, 2016). Most cortisol-lowering products, including many marketed to women, lack the research to back their promises.
What genuinely helps with stress and its effects is unglamorous:
- Steady, sufficient sleep, since sleep and cortisol rhythm are tightly linked
- Regular exercise that challenges you without overtraining
- Stress management such as slow breathing, time outdoors or activities you find calming
- Sensible limits on heavy alcohol and very high caffeine
Testing
Cortisol can be measured in blood, saliva or urine, and doctors sometimes use special tests that check how it responds to a trigger. Testing is done to investigate a suspected condition, such as the symptoms above, not to fine-tune day-to-day stress. Because of the daily rhythm, results must be read alongside the time of day and your overall picture, which is a job for a doctor rather than a home kit.
When to see a doctor
See your doctor if you have symptoms that suggest a genuine cortisol problem, such as unexplained central weight gain with skin and muscle changes, or ongoing fatigue with weight loss and low blood pressure. For everyday stress, the useful path is the lifestyle basics, not chasing a cortisol number.
Frequently asked questions
What does cortisol do?
Cortisol is your main stress hormone, made by the adrenal glands. It helps your body respond to stress, but it also regulates metabolism, blood sugar and blood pressure, calms inflammation, and helps control your sleep-wake cycle. It affects nearly every tissue in the body.
What are the symptoms of high cortisol?
Genuinely high cortisol, as in Cushing's syndrome, can cause weight gain around the middle and face, thin skin that bruises easily, muscle weakness, high blood pressure and irregular periods. This is uncommon and quite different from everyday stress, which does not usually push cortisol to those levels.
How do you lower cortisol naturally?
The evidence-based basics are steady sleep, regular exercise that is not excessive, managing stress with methods like breathing or time outdoors, and limiting heavy alcohol and very high caffeine. There is no proven benefit from most 'cortisol-lowering' supplements marketed online.
Can you test your cortisol levels?
Yes, through blood, saliva or urine, and timing matters because cortisol is naturally highest in the morning and lowest at night. Testing is used to investigate specific conditions, not to fine-tune everyday stress, and results need a doctor to interpret against the time of day.
References
- Adrenal fatigue does not exist: a systematic review · BMC Endocrine Disorders, 2016
- Cortisol: what it is, function, symptoms and levels · Cleveland Clinic
- Cortisol test: what it is, purpose, types and results · Cleveland Clinic