What is cortisol, and why does it matter?

Cortisol is a hormone made by two small glands that sit on top of your kidneys. It helps you wake up, handle stress, keep your blood sugar steady and calm down inflammation. It's naturally highest in the morning and lowest at night — that's why sleep matters so much. Everyday stress and tiredness are almost never a real cortisol problem. Genuine imbalances are uncommon and need a GP to spot.

What cortisol actually is What it does for you Your daily cortisol rhythm Cortisol and stress When cortisol is too high When cortisol is too low Cortisol, weight and belly fat How to keep cortisol balanced Cortisol as a medicine When to see your GP

Cortisol is a hormone — a chemical messenger your body uses to send instructions around. It's made by your adrenal glands , two little glands that sit on top of your kidneys. How much you make is controlled by a constant back-and-forth between your brain and those glands. Your brain says "make a bit more" or "ease off," and your adrenal glands respond. Most of the time this happens completely without you noticing.

Cortisol has a lot of day jobs. The main ones: Helps you wake up and feel alert in the morning Powers your "fight or flight" response when you're under pressure Keeps your blood sugar steady through the day Helps control your blood pressure Calms down inflammation and helps manage your body's response to illness Read more: what does cortisol do in your body?

Cortisol isn't steady all day — it runs on a clock. It's highest in the morning , usually within about half an hour of waking up, which is what helps get you going. Then it slowly drops through the day and is at its lowest around midnight . This is why a wrecked sleep schedule, late nights or shift work can throw your cortisol out of its natural pattern — and why fixing your sleep is often the simplest place to start. Read more: cortisol, sleep and your body clock

When something stressful happens, your body releases a burst of cortisol to help you cope — sharper focus, more energy, ready for action. That's a good thing. It's meant to spike and then settle back down. The problem is modern life, where stress sometimes never really switches off. If your body keeps the tap running for weeks and months, that's when ongoing stress can start to wear you down. Read more: why cortisol is called the stress hormone

Now and then, cortisol can stay too high for the wrong reasons. The signs tend to build up slowly: Weight gain around your tummy and face, with thinner arms and legs Purple or pink stretch marks across your tummy Bruising very easily Feeling weak, and high blood pressure The most common reason is taking steroid medicine for a long time. More rarely, it's caused by a condition called Cushing's syndrome . Read more: signs your cortisol might be too high

Cortisol can also drop too low. This is less common, but worth knowing the signs: Tiredness that rest doesn't fix Losing weight and appetite without trying Craving salty food Feeling dizzy when you stand up, and patches of darker skin Persistently low cortisol can be caused by a condition called Addison's disease , which needs a doctor to diagnose and treat. Read more: signs of low cortisol

You'll see a lot online about "cortisol belly." There's a grain of truth in it — when cortisol stays high for a long time, it can nudge your body to store fat around your middle and bump up your appetite. But it's more complicated than the internet makes out. For most people, weight is driven by sleep, food, movement and stress all together — not cortisol on its own. There's no magic "cortisol fix" for belly fat. Read more: does cortisol cause weight gain?

The good news: the everyday habits that keep cortisol happy are the same ones that are good for the rest of you. No fancy supplements needed. Sleep — a regular sleep schedule is the single biggest lever Move your body — but don't overdo it; too much hard training can push cortisol up Eat steadily — regular meals help keep your blood sugar (and cortisol) even Wind down — anything that genuinely relaxes you, from a walk to prayer to breathing exercises Read more: how to lower cortisol naturally

Here's a bit most people don't realise: some very common medicines are man-made versions of cortisol . Doctors use them to calm inflammation or to replace cortisol when the body isn't making enough. You might know them by name: hydrocortisone , prednisolone and dexamethasone. They work well, but they come with one golden rule — never stop them suddenly without your doctor's guidance.

If you take steroid tablets like hydrocortisone or prednisolone, your body may be relying on them for its cortisol. Never stop suddenly , and follow your sick-day rules if you become unwell. Keep your steroid emergency card on you if you've been given one.

Everyday tiredness and stress don't need a test. But see your GP if symptoms build up over weeks. And call 999 if someone is very unwell with severe vomiting, confusion, sudden bad pain or collapse — this can be a rare emergency called an adrenal crisis. Read the full guide: when to worry about your cortisol

Is cortisol bad for you? Not at all — you couldn't live without it. It only becomes a problem if it stays too high or too low for a long time, which is uncommon. Can I lower my cortisol naturally? For everyday stress, yes — better sleep, regular movement, steady meals and winding down all help. You don't need special supplements or tests. Do I need a cortisol test? Usually not. A GP will only arrange one if your symptoms point to a real imbalance. A single home test is hard to make sense of on its own. What's the difference between Cushing's and Addison's? In simple terms: Cushing's syndrome is too much cortisol, Addison's disease is too little. Both are uncommon and both need a doctor to diagnose.

What does cortisol do? The stress hormone Signs of high cortisol Signs of low cortisol Lower cortisol naturally Cortisol & weight When to see your GP Cushing's syndrome Addison's disease Hydrocortisone

⚠ Placeholders — Review Board to confirm NHS. Cushing's syndrome . [Confirm URL & access date] NHS. Addison's disease . [Confirm URL & access date] Society for Endocrinology. Cortisol — You and Your Hormones . [Confirm URL & access date] NICE Clinical Knowledge Summaries. Corticosteroids & adrenal insufficiency . [Confirm URL & access date] NHS. Steroid tablets & the steroid emergency card . [Confirm URL & access date]