Drugs associated with decreased vitamin B12:
(1) metformin
(2) proton pump inhibitors
(3) histamine H2 receptor antagonists
The risk with metformin increases with:
(1) higher daily doses
(2) long-term therapy (>= 4 years)
(3) concurrent therapy with a sulfonylurea
(4) concurrent therapy with other drugs listed above
A patient with one or more of these risk factors should be screened for vitamin B12 deficiency, especially if there is anemia or neuropathy.
Therapy for vitamin B12 deficiency involve:
(1) discontinuing one or more of the implicated drugs
(2) oral or parenteral vitamin B12 supplementation
