APO-METFORMIN - TAB 500MG
ATC Code
A10BA02
Warning
Metformin can cause Vitamin B12 deficiency
Really. There are many postulated mechanisms - the most commonly cited being that metformin interferes with intestinal calcium availability which leads to reduced absorption of B12 (a calcium-dependent process).
Use for 3 years or more and higher doses were shown to be risk factors in a small nested case-control study. Other suspected contributors are advancing age and a vegetarian diet.
There is controversy about how to treat it. The efficacy of folic acid and vitamin B12
supplementation is debatable though malabsorption of vitamin B12 is likely reversible
within 2-8 weeks after stopping metformin.
Monitoring of vitamin B12 levels in patients on metformin should be done annually or every 2-3 years according to opinions of various authors. This should continue for at least 10 years after cessation according to one study since symptoms may be delayed.
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