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.
Blood B12 Level: Not Reliable. A serum B12 (sB12) level below the normal range indicates that B12 levels are becoming depleted. However, as described below, a sB12 level in the normal range does not ensure that B12 levels are healthy.Unfortunately, medical practitioners still use serum B12 to evaluate function, even of vegans.lood B12 Level: Not Reliable. A serum B12 (sB12) level below the normal range indicates that B12 levels are becoming depleted. However, as described below, a sB12 level in the normal range does not ensure that B12 levels are healthy.