If you experience headaches while taking metformin, it is possible that you are allergic to some inactive ingredient, although some patients do report headaches while taking metformin. It is more likely that your body is still adjusting to the metformin. You may want to try taking it at night or a time when you don't need to work. It is best to take it with a meal. Try giving the medication a couple more weeks for your body to adjust. If the headaches have not decreased, talk to your doctor about how they are affecting your quality of life and your work and discuss your other treatment options.