Summary: Recent years have brought more and more papers discussing the potential influence of metformin on vitamin B12, folic acid, homocysteine and methylmalonic acid concentration, the direction of this relationship and its implications in daily practice. Due to widespread use of metformin, the topic is definitely worth attention.
Does metformin reduce the concentration of vitamin B12 in the plasma? If it does, then how? What are the effects of cobalamin deficiency? Does vitamin B12 deficiency due to metformin use cause the development of diabetic neuropathy? And does metformin perhaps show neuroprotective activity? Should routine vitamin B12 concentration periodic tests be introduced into daily practice? And what about supplementary treatment?
The paper's authors ask the questions and try to find answers as accurately as possible. Even though such scientific papers have been published for many years, we still lack strong evidences to support most of the above-mentioned ideas. Most of the research yields observational papers, mostly cross-sectional. Maybe it is enough to suspect the influence of metformin on decreasing vitamin B12 levels, but it is difficult to answer more precise questions. It is also not easy to present unambiguous answers and simple recommendations. Nevertheless, the present text should help familiarize readers with the topic, offering a review of the current state of knowledge, and might suggest directions of further research.