I'm not at all sure, but I don't think Metformin is actually licensed for non-diabetics other than as an appetite suppressant for those needing to lose a lot of weight. (It started out life as an appetite suppressant back in the 50s I believe) Certainly at my Practice it isn't generally prescribed if the diagnosis HbA1c is 53 or less.
I must admit that metformin has been prescribed for pre diabetics mainly in the USA
Prediabetes is, for many people, a confusing condition. It’s not quite Type 2 diabetes — but it’s not quite nothing, either. So how concerned should you be about it?
For years, the jargon-filled names given to this condition — impaired fasting glucose (IFG) and impaired glucose tolerance (IGT) — may have made the task of taking it seriously more difficult. But in 2002, the American Diabetes Association (ADA), along with the U.S. Department of Health and Human Services, inaugurated the term “prediabetes” to convey the likely result of not making diet or lifestyle changes in response to this diagnosis. In 2003, the threshold for prediabetes was lowered from a fasting glucose level of 110 mg/dl to one of 100 mg/dl.
Then, in 2008, the American Diabetes Association (ADA) began recommending the drug metformin for some cases of prediabetes — specifically, for people under age 60 with a very high risk of developing diabetes, for people who are very obese (with a body-mass index, or BMI, of 35 or higher), and for women with a history of gestational diabetes. The ADA also said that health-care professionals could consider metformin for anyone with prediabetes or an HbA1c level (a measure of long-term blood glucose control) between 5.7% and 6.4%.
But according to a recent study, metformin is still rarely prescribed for prediabetes. The study, published in April in the journal Annals of Internal Medicine, found that only 3.7% of people with prediabetes were prescribed metformin over a three-year period, based on data from a large national sample of adults ages 19 to 58. According to a Medscape article on the study, 7.8% of people with prediabetes with a BMI of 35 or higher or a history of gestational diabetes were prescribed metformin — still a very low rate for the highest-risk groups, in which evidence for the benefits of metformin is strongest. It appears that most doctors simply aren’t following the ADA’s guidelines or aren’t aware of them, as they relate to prediabetes.
http://www.diabetesselfmanagement.com/blog/metformin-for-prediabetes/
Edit to add this link'
http://link.springer.com/article/10.1007/s40265-015-0416-8
