A commonly-used drug to control Type 2 diabetes could double the risk of bladder cancer, a study indicates.
The results show that more than two years daily exposure to pioglitazone doubles the risk of bladder cancer.
The researchers based in Canada analysed the medical records of more than 115,000 people across the UK who were given the drug over an 11-year period and found there were up to 137 extra cases of bladder cancer per 100,000 person years.
Writing online in the British Medical Journal, the researchers, from the Jewish General Hospital in Montreal, Canada, said their results "provide evidence that pioglitazone is associated with an increased risk of bladder".
They noted that in absolute terms, the risk of getting bladder cancer was still small in those taking pioglitazone.
Dr Iain Frame, director of research at Diabetes UK, told the Telegraph: “We would reassure people that overall the risk of developing bladder cancer while taking pioglitazone is low and to stress that although taking the drug in the circumstances outlined has been associated with bladder cancer it has not been shown to cause bladder cancer.
"We advise that people taking pioglitazone should continue to take it and discuss any concerns they have with their health care professionals."