Vitamin B12 deficiency

by Dr. Lazowski

Vitamin B12 deficiency can present as weakness, fatigue and bilateral lower-extremity neuropathy. The popular belief among physicians is that an intramuscular injection is needed for adequate supplementation of vitamin B12. The reason for this is because there is an inadequate secretion of gastric intrinsic factor necessary for vitamin B12 absorption. Studies from the 1950s suggested that vitamin B12 must be administered by injection to effectively treat this condition. Newer investigations (Acta Med. Stand. 1978;204:81-4; Blood 1998;92:1191-8) show that oral vitamin B12 intake in the amount 1000-2000 micrograms daily leads to higher blood levels of vitamin B12 than those achieved by intramuscular injection. In a survey of internists, 94% were not aware of the availability of oral therapy for B12 replacement, and 88% said an oral replacement form of B12 would be useful in their practice (JAMA 1991;265:94-5). Oral supplementation of vitamin B12 is an effective and economical initial treatment option.