Metformin has a strong claim to being one of the most influential medicines of the past century. For decades, it has underpinned the treatment of type 2 diabetes, helped millions of people control their blood sugar, and inspired a second life in research on everything from ageing and cancer to heart health and fertility.

Its story begins not in a laboratory but in a plant, galega officinalis, also known as French lilac or goat’s rue. For centuries, the plant was used in folk remedies for symptoms we now recognise as associated with diabetes, including excessive thirst and frequent urination. In the early 20th century, scientists isolated blood sugar-lowering compounds from it. After years of refinement and testing, metformin emerged as a relatively safe and effective medicine, and was introduced in the UK in the late 1950s.

Large clinical trials, which are carefully designed studies in people to test how well treatments work, confirmed what many doctors already suspected. Metformin was not only effective at lowering glucose, the body’s main form of sugar, but also at reducing diabetes-related complications. It became the main treatment for type 2 diabetes across much of the world.

Metformin is a biguanide drug, a class of medicines that lowers blood sugar, and it works by helping the body use insulin more effectively. Insulin is the hormone that helps move glucose from the bloodstream into cells for energy. Metformin reduces the amount of glucose released by the liver, improves the way muscles take up glucose from the blood, and reduces........

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