NHS guidance warns people who take statins to call 999 immediately if they notice any of a number of symptoms. Statins are a group of medicines that can help lower the level of low-density lipoprotein (LDL) cholesterol in the blood.

LDL cholesterol is often referred to as "bad cholesterol", and statins reduce the production of it inside the liver. High levels of LDL cholesterol can be dangerous and can lead to higher risk of strokes, heart attacks, angina, and coronary heart disease.

People who are prescribed statins usually take them once a day. As with other medications, some people who take statins experience side effects, although most do not.

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Depending on which type of statin you are taking, common side effects can include nausea, headaches, nosebleeds, cold-like symptoms, a sore throat, constipation, diarrhoea, protein in urine, flatulence, stomach pain, and feeling weak or dizzy. NHS advice adds: "Talk to your doctor or pharmacist if you get any side effects at all, and if they bother you or do not go away. Your doctor may recommend trying a lower dose of pravastatin or a different statin."

However, the NHS also warns of serious side effects, which require emergency medical attention. Its guidance for atorvastatin (Lipitor), pravastatin (Lipostat), rosuvastatin (Crestor), and simvastatin (Zocor), states you should stop taking your medication and call 111 or a doctor straight away if you experience any of the following symptoms:

• unexplained muscle pain, tenderness, weakness or cramps – as these can be signs of muscle breakdown and kidney damage
• a skin rash with pink or red blotches, especially on the palms of your hands or soles of your feet – as this could be a sign of erythema multiforme
• the whites of your eyes turn yellow, or your skin turns yellow, although this may be less obvious on brown or black skin, or if you have pale poo and dark pee – these can be signs of liver problems
• severe stomach pain – this can be a sign of acute pancreatitis
• a cough, feel short of breath, and are losing weight – this can be a sign of lung disease
• weakness in your arms or legs that gets worse after activity, or if you get double vision, drooping eyelids, problems swallowing or shortness of breath - these can be a sign of myasthenia gravis

You should call 999 or go straight to A&E if you develop severe breathing or swallowing problems. Certain other signs may mean you've had a serious allergic reaction and should call for an ambulance:

• your lips, mouth, throat or tongue suddenly become swollen
• you suddenly become very confused, drowsy or dizzy
• you're breathing very fast or struggling to breathe (you may become very wheezy or feel like you're choking or gasping for air)
• your throat feels tight or you're struggling to swallow
• your skin, tongue or lips turn blue, grey or pale (if you have black or brown skin, this may be easier to see on the palms of your hands or soles of your feet)
• a child is limp, floppy or not responding like they normally do (their head may fall to the side, backwards or forwards, or they may find it difficult to lift their head or focus on your face)
• someone faints and cannot be woken up

You or the person who's unwell may also have a rash that's swollen, itchy, raised, peeling, or blistered.