Overdose of which vitamin is dangerous vita, vitd, vitb1, folic acid?

A & D- very rare: One can only overdose on fat soluble vitamins (a, d, e) except vit. B6 (which should be limited to 250 mg/day). But it takes huge amounts to overdose. The average adult would need to take about 2 million units of a to overdose, or 200, 000 iu/day for several months. Vit d toxicity is rare unless one takes at least 40, 000 iu/day for months. See http://emedicine.Medscape.Com/article/819426-overview.