[Oral better than parenteral supplementation of vitamin B12].Ned Tijdschr Geneeskd. 2009; 153:B485.NT
Vitamin B12 deficiency occurs in 5-10% of the Dutch population. Serum vitamin B12 levels should be determined in patients with haematological or neurological disorders such as megaloblastic anaemia or neuropathy, and in patients with risk factors for vitamin B12 deficiency such as atrophic gastritis or intrinsic factor-deficiency. The aim of this article was to explicate the data from the literature on the efficacy of oral versus parenteral vitamin B12 supplementation. Two randomised, controlled trials have shown that oral supplementation of 1000-2000 microg/day of vitamin B12 is equally effective in raising serum vitamin B12 levels as a standard parenteral dosing schedule. Moreover, the effects on clinical endpoints were comparable. Several dose-finding studies have been performed, showing that the minimal effective oral dose is 647-1032 microg/day. It is recommended that patients with vitamin B12 deficiency be prescribed 1000 microg/day vitamin B12 orally, unless they have problems with swallowing or treatment compliance or have severe clinical symptoms. In that case parenteral administration is indicated.
