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.
The Dietary Reference Intake (DRI) of vitamin B12 varies depending on your age and your particular needs. In males and females ages 14 and over, the DRI is 2.4 micrograms (mcg) per day. That number goes up to 2.6 mcg during pregnancy and 2.8 mcg during breast-feeding.Supplementation of higher levels of vitamin B12 may be recommended for certain people over age 50 who have trouble absorbing the vitamin from foods.n males and females ages 14 and over, the DRI is 2.4 micrograms (mcg) per day. That number goes up to 2.6 mcg during pregnancy and 2.8 mcg during breast-feeding. Supplementation of higher levels of vitamin B12 may be recommended for certain people over age 50 who have trouble absorbing the vitamin from foods.