High doses of cholesterol-lowering pills can increase the risk of type 2 diabetes, researchers warn.
They have found that patients taking intensive courses of statins were 12 per cent more likely to get the disease.
But experts pointed out that that the risk was far outweighed by the substantial benefits – the pills were shown to reduce the likelihood of heart attacks by 16 per cent.
More than seven million people in Britain now take statins – as many as one in three adults over the age of 40.
It is not known exactly how many are on high doses of more than 80 miligrams a day, but it is likely to only be a small proportion most at risk of heart attacks and strokes.
Researchers from the University of Glasgow looked at five previous studies involving 32,700 patients.
They were either on high doses of 80 mg or moderate doses of 20mg to 40 mg.
The study, published in the Journal of the American Medical Association found there were 149 extra cases of type 2 diabetes recorded amongst the patients on high dose statins, representing a 12 per cent risk.
The authors concluded: ‘Our findings suggest that clinicians should be vigilant for the development of diabetes in patients receiving intensive statin therapy.’
Statins are extremely effective in lowering levels of cholesterol, the fatty substance in the blood that clogs up arteries leading to heart attacks and strokes.
Last night experts urged people not to stop taking the pills on the basis on this evidence.
Professor Peter Weissberg, medical director of the British Heart Foundation, said: ‘Nobody should stop taking their prescribed statins because of the evidence shown in this research.
‘Statins play a vital role in protecting the hearts of many, many people and the benefits still far outweigh any risks associated with diabetes.
‘The increased risk occurred predominantly in those taking a high dose of these drugs, whereas most people are on low or moderate doses.
‘Always speak to your doctor if you have any concerns about your medication. Don’t simply stop taking it.’
Experts also pointed out that patients on statins may have been at higher risk of diabetes in the first place if they were overweight.
Libby Dowling, clinical advisor at Diabetes UK said: ‘This analysis of previous studies has found that high doses of statins increase the risk of developing Type 2 diabetes, yet at the same time reduce the risk of heart disease.
‘What we don’t know from this research is whether the people being prescribed the high-dose statins were overweight as having a large waist puts you at increased risk of developing Type 2 diabetes anyway.