Lithium can definitely cause headaches, and a dose increase may increase the frequency of those headaches, but I am not sure about lithium causing migraines specifically. I run a blood level of about 0.5 and can count on 3-4 headaches a week requiring ibuprofen or more. I get a classic migraine about once every 1-2 months that I take imitrex for. I have read that migraines are more common among those with BPII but I have not heard of an increased prevalance amongh type I bipolar patients.