Steroids, also called corticosteroids, are anti-inflammatory medicines used to treat a range of conditions.
They're different from the anabolic steroids used by athletes and body builders to improve their performance.
Steroids come in many different forms.
The main types are:
Most steroids are only available on prescription, but a few (such as some creams or nasal sprays) can be bought from pharmacies and shops.
Steroids don't tend to cause significant side effects if they're taken for a short time or at a low dose.
But sometimes they can cause unpleasant side effects, such as an increased appetite, mood changes and difficulty sleeping. This is most common with steroid tablets.
The side effects will usually pass once you finish the treatment, but don't stop taking your medicine without speaking to your doctor. This can cause further unpleasant side effects (withdrawal symptoms).
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You can report any suspected side effect to a UK safety scheme.
Steroids can be used to treat a wide range of conditions, including:
Steroids are a man-made version of hormones normally produced by the adrenal glands, two small glands found above the kidneys.
When taken in doses higher than the amount your body normally produces, steroids reduce redness and swelling (inflammation). This can help with inflammatory conditions such as asthma and eczema.
Steroids also reduce the activity of the immune system, the body's natural defence against illness and infection.
This can help treat autoimmune conditions, such as rheumatoid arthritis or lupus, which are caused by the immune system mistakenly attacking the body.