We're in the grip of a diabetes epidemic. The NHS spent more than half a billion pounds on medication for it in 2009. Patients trust that these drugs are safe, but does one come with a hidden cost to health? Shelley Jofre investigates the rise and fall of Avandia, until recently one of the UK's best-selling diabetes drugs, and asks whether the medicine's regulator is putting the interests of the drugs industry before patients.