Metformin, sold under the brand names of Bolamyn, Diagemet, Glucient, Glucophage, Metabet, Obimet, Gluformin, Dianben, Diabex, Diaformin, Metsol, Siofor, Metfogamma (and many others) is a prescription-only medication used in the treatment of Type 2 Diabetes.

It's been in use worldwide since 1957, and the prescription rates are now around 78 million in the US alone. It can reduce a diabetic person's (excess) blood glucose by 30%.

It was originally derived from the French lilac or Goat's rue (Galega officinalis) which has been used in herbal remedies for several centuries.

Its mechanism of action is unknown. There are multiple proposals as to how it might operate - including as an appetite suppressant. See Wikipedia

Metformin is currently being investigated, with promising results, as a treatment for :
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Parkinson's diseaseplugin-autotooltip__plain plugin-autotooltip_bigParkinson's disease

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There is no explanation for its apparent efficacy in treating any of these conditions.