Hello, i'm taking vitamin b2 at 400mg a day for migraines. could that be causing my recent constipation? i am also taking 400mg of magnesium.

Doubtful: Vitamin B2 shouldn't cause constipation. But magnesium is helpful for many patients' constipation. You can increase the magnesium to twice a day if using it once a day doesn't fix your constipation. Try them for 3 months, and if your migraines aren't less frequent and less severe, please give me a call and we can discuss additional preventive meds.