Iron supplement and headache

I recently had blood work done because I was feeling ridiculously exhausted (napping after waking up in the morning) and my midwife said my iron was low. She gave me a supplement and I'm on day 3 of 1 pill a day but I have a horrible headache right now. She also prescribed Vit C with it which is fine but I'm wondering if I'm getting too much? This is the type of headache I used to get prepregnancy when I would try to take a daily multivitamin..