Recently a friend of mine called and asked if I could prescribe Metformin for a patient who came from Europe to visit my friend as the visitor forgot to bring the same. I called in the medicine, oral B12 tablets and advised him to take calcium supplements. He was not aware that he needed to be on it which prompted this post.

References
1 Age and aging,2006/ Published by Oxford university press / British Geriatric Society /Kin Wah Liu Shatin hospital/ Hongkong
2 Diabetes Care Volume 23,no 9, Sept 2000. ( Bauman et al Mount Sinai School of Medicine NY.
3 BMJ 2010;340:c2181

B12 deficiency associated with prolonged metformin intake is less commonly recognized ( 10-30% ) as opposed to lactic acidosis. Diabetics have slow intestinal transport causing bacterial overgrowth and B12 malabsorption. The B12 -intrinsic factor complex uptake by ileal cell membrane is calcium dependent. Metformin induced B12 defcy can be reversed by administering calcium.

Routine assessment of Vitamin B12 ( holo TC II ) during long term treatment with metformin is recommended.