I get migraines occasionally (full-blown ones) and a different type of migraine that is more like a moderate headache that just lasts for 3 days no matter what I take. Strangley enough, I haven't had one since I started low carbing 18 months ago. My DH also gets something called cluster migraines...brief, but very intense. I've seen him get one while walking across the room and it literally dropped him to his knees. He says it feels like someone just hit him in the head with a hammer; then 15 or 20 minutes later, it's gone. He hasn't had an attack since he started low carbing, either. It could be completely random, but it could also be triggered by something you are sensitive to like grains, dairy or any other food or even environmental factors, for that matter and would probably be very difficult to pinpoint exactly unless you keep a fairly accurate food journal and then look at what you were eating the day or so before you got one. If you're really determined to track down any cause and effect, it might be a place to start, though.