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Steroids, also called corticosteroids, are anti-inflammatory medicines used to treat a range of conditions.
They're different from anabolic steroids, which are often used illegally by some people to increase their muscle mass.
Types of steroids
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.
Side effects of steroids
Steroids do not 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 do not stop taking your medicine without speaking to your doctor. Stopping a prescribed course of medicine can cause further unpleasant side effects (withdrawal symptoms).
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You can report any suspected side effect to the Yellow Card Scheme.
Uses for steroids
Steroids can be used to treat a wide range of conditions, including:
How steroids work
Steroids are a man-made version of hormones normally produced by the adrenal glands which are 2 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, which is 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.