Metformin (1,1-dimethylbiguanide hydrochloride), is today, the most prescribed oral medicine for type 2 diabetes , taken by millions of people every day. It is inexpensive, effective, and widely available: tablets of 500 mg cost barely a rupee each. For a country where diabetes care is a major household expense, metformin remains one of the few drugs that combines affordability with scientific reliability. Metformin, listed among the World Health Organization’s essential medicines since 2011, is generally safe but may cause mild gastrointestinal upsets, give a metallic taste, or, rarely, may cause lactic acidosis in kidney-impaired patients. Yet its story spans over a century of neglect, rediscovery, and vindication.

The first clue

The roots of metformin can be traced to a herb called

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