Magnesium (non-prescription) has been utilized in the treatment of vascular headache. It is most commonly recommended as a supplement in the preventative treatment of migraine and sometimes used for cluster headache. Few credible studies are available, but some patients and physicians attest to its helpfulness. It is thought to effect cerebral vascular changes. The average recommended dose is 200-500 mg/day. In high or excessive doses, magnesium can cause significant and sometimes serious toxic reactions. Some clinicians have utilized magnesium in the abortive treatment of acute migraine, particulary with pregnancy when options are limited.