More than 800 million adults have diabetes worldwide — almost twice as many as previous estimates have suggested — and more than half of those aged over 30 who have the condition are not receiving treatment, according to a new study.

The study published in The Lancet found the global prevalence of diabetes has doubled since 1990 to 14% from around 7%, and the authors suggest the increase has been driven largely by rising cases in low- and middle-income countries.

Although there are far more cases, treatment rates in those regions have barely increased, the authors said, while things have improved in some higher-income countries — leading to a widening treatment gap.