Description
Vitamin B12 deficiency is associated with
metformin treatment, and can result in raised plasma
homocysteine, a well established cardiovascular risk
factor. The mechanism of vitamin B12 deficiency in
these patients is not well defined, but has been linked
to relative hypocalcaemia. The question of oral B12
replacement has been raised, and studies have shown
that oral replacement with high doses (1000-
2000mcg/day) may be necessary for normalisation of
B12 and homocysteine levels. While this has not been
directly assessed for diabetics with metformin-induced
B12 deficiency, we would recommend a trial of
replacement with high dose oral cyanocobalamin, with
calcium replacement if appropriate. Patients in whom
this treatment strategy fails should be treated with
standard intramuscular hydroxycobalamin replacement
as for pernicious anaemia.
