To be honest I am not sure. I was given them Saturday by the gp and not really any further information so in the dark a bitHi Mark, it is a common side effect with metformin but usually goes away fairly soon as your body gets used to it. Are you on prolonged release metformin? If not ask about changing to it. The side effects are less severe. It may also reoccurre if you increase the dose. Hopefully the DN will be able to help.