| A vitamin B12 deficiency is often diagnosed (sometimes incorrectly) as AD. Unlike most other vitamins, oral forms of vitamin B12 are very poorly absorbed (only 5-10% of an oral dose actually makes it into the bloodstream). Sublingual B12 fares somewhat better, but still less than 20% is absorbed, so the effective dose is 4 or more 1000 mcg. sublingual tablets daily. For severe deficiencies, the intramuscular IM route, with 100 % absorption, is best. There is no reason to worry about getting too much B12; if it happened to you, you’d be the first case in medical history; it just simply has never happened...ever! Deficiency states, on the other hand, are very common. | 
