It was Christmas week 1990 in Oakland. Steven Bloom was wandering through The Lot, that timeless gathering of hippies that springs up in the parking lot before every Grateful Dead concert, when a Deadhead handed him a yellow flyer.
Because of the general safety of the vitamin, upper limits for normal intake do not exist. If your blood values for the vitamin fall below a range of 170 to 250 picograms per milliliter, you may develop a B12 deficiency.
Yes, safe dose!: In general one has to take at least 40, 000 iu of vit d for a prolonged period to approach toxic levels. It is considered safe to take up to 10, 000 iu/day. You could get a blood test of your levels to see where you are at. While normal range is 30-100, optimal range is probably above 50.