Multivitamins refers to a combination of different vitamins which are normally found in foods and other natural sources. Multivitamins can have many side effects, and headache is one of them. It can happen to anyone who is taking a multivitamin. Normally, if a multivitamin is not taken in accordance with your doctor's instructions, it causes such side effects. It has nothing to do with your migraine. There is another factor that you need to consider regarding your migraine. Normally synthetic multivitamins are known to create problems for people. So I suggest you use a food based multivitamin which will minimize the side effects, if any.