I'm looking around for supplements which will help with sleep and have been looking at niacin. From what I've read so far, two queries come to mind: 1 I've found several references to caution with niacin if you have gallbladder disease and I have gallstones. Anyone understand the reason for the caution? I understand it's related to cholesterol but that's as far as I've got.... 2 The flushing effect I believe is caused by dilation of blood vessels and I wonder if I should therefore avoid as I get migraines? Anyone found niacin caused headache/migraine?