Pharmacy Clinical Pearl of the Day: Long-Term Metformin Use and Vitamin B12 Deficiency

Clinical Pearl of the Day:

Long term use of metformin can cause vitamin B12 deficiency.

Explanation:

• The mechanism by which metformin reduces the vitamin B12 levels is still unknown, but the most likely hypothesis is that metformin interferes with the calcium-dependent membrane action responsible for vitamin B12 intrinsic factor absorption, which occurs in the terminal ileum.
• Patients on metformin should check their B12 levels on regular basis, possibly annually, to make sure it is within a normal range.
• The normal level of vitamin B12 in the bloodstream is generally between 190 and 950 picograms per milliliter (pg/ml)

Reference: Association between metformin dose and vitamin B12 deficiency in patients with type 2 diabetes (nih.gov)