What is the best medicine to lower your blood sugar?

No Single agent: There is no single best medication to lower sugars. Most people will need multiple agents to lower their sugars (sometimes Insulin may be needed).

Depends: It depends upon many, many factors. Usually metformin is the most commonly prescribed medication. You also need education, good medical advice, diet, exercise, weight loss, control of BP and cholesterol, monitoring and many other things to make sure your diabetes is well controlled.