Metformin is the most commonly prescribed medication for the treatment of diabetes in the UK. It is also one of the most prescribed drugs overall in the UK. As with other drugs, it is possible to experience side effects during the treament or medicine may not be suitable. Metformin can commonly cause gastrointestinal side effects and this very often leads to switching to another drug. Although there are many type-2 diabetic drugs, patients would be offered metformin alternatives according to the national guidance on the management of type 2 diabetes. Today I will summarise metformin alternative drugs, which may be prescribed to type 2 diabetic patients who cannot tolerate metformin.