Steroids (corticosteroids) explained: benefits, risks and the steroid card

What corticosteroids are (and are not)

Corticosteroids are man-made versions of cortisol, a hormone your own adrenal glands make. They are not the same as the anabolic steroids some people misuse to build muscle — the two are often confused but work entirely differently. Medical corticosteroids reduce inflammation and quieten the immune system, which is why they help so many conditions: flare-ups of asthma and COPD, rheumatoid arthritis and other inflammatory joint diseases, skin conditions, allergies, and many more. They come in several forms — tablets, injections, inhalers, creams, eye drops and nasal sprays — and the form matters a great deal for how much of the body is affected, as we explain below.

Short courses versus long-term use

A short course of steroid tablets — for example to settle an asthma flare or a bad flare of inflammation — is usually well tolerated and can be stopped fairly straightforwardly when it has been brief. The picture changes with longer-term use. When you take steroids for more than a short while, the body senses there is plenty of cortisol around and the adrenal glands wind down their own production. This is why longer-term steroids cannot simply be stopped: the body can no longer make enough of its own cortisol quickly, and stopping abruptly can trigger a dangerous shortage. Longer use also brings more side effects, so it is always balanced carefully against the benefit for your condition.

Never stop suddenly: the steroid emergency card and sick-day rules

If you take steroids long-term, never stop them abruptly — this can cause adrenal crisis, a serious drop in essential hormones that can be life-threatening. Instead, they are reduced gradually under guidance so your adrenal glands can recover. You should carry a steroid emergency card (and ideally medical-alert jewellery) so that, in an emergency, healthcare staff know you depend on steroids. When you are unwell — with a fever, vomiting, an infection or before surgery — your body needs more cortisol than usual. "Sick-day rules" mean your steroid may need to be temporarily increased, and if you cannot keep tablets down you may need an injection and urgent care. Know your plan before you need it.

Side effects and why the form matters

Longer-term steroid use can affect many parts of the body: thinning of the bones, raised blood sugar (sometimes tipping into diabetes), changes in mood or sleep, a greater chance of infections, weight gain and changes in appearance, and raised blood pressure. These risks rise with higher amounts and longer use, which is why the aim is always the smallest effective treatment for the shortest sensible time, with monitoring. Reassuringly, steroids that act mainly where they are applied — inhaled corticosteroids for the lungs and topical corticosteroids for the skin — deliver the medicine locally and reach the rest of the body far less, so they carry fewer whole-body effects than steroid tablets taken long-term.