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Abstract: >Years of use of the antidiabetic drug metformin has long been associated with the risk of vitamin B12 (B12) deficiency in type 2 diabetes (T2D) patients, although the underlying mechanisms are unclear. Accumulating evidence has shown that metformin may exert beneficial effects by altering the metabolism of the gut microbiota, but whether it induces human B12 deficiency via modulation of bacterial activity remains poorly understood. Here, we show that both metformin and the other biguanide drug phenformin markedly elevate the accumulation of B12 in E. coli. By functional and genomic analysis, we demonstrate that both biguanides can significantly increase the expression of B12 transporter genes, and depletions of vital ones, such as tonB, nearly completely abolish the drugs’ effect on bacterial B12 accumulation. Via high-throughput screens in E. coli and C. elegans, we reveal that the TetR-type transcription factor RcdA is required for biguanide-mediated promotion of B12 accumulation and the expressions of B12 transporter genes in bacteria. Together, our study unveils that the antidiabetic drug metformin helps bacteria gather B12 from the environment by increasing the expressions of B12 transporter genes in an RcdA-dependent manner, which may theoretically reduce the B12 supply to T2D patients taking the drug over time.

That's why you take B12 supplements while on metformin

Yeah it’s not that simple. My dad is on B12 injections and he’s still anemic

I was never told about the need to supplement B-12. Good information.

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I was taking half a gram of extended release metformin daily, for longevity, for about a year, until I started feeling pins and needles (peripheral neuropathy) in my hands and feet. I then remembered I had read about metformin and B12 deficiency, and I immediately stopped it and started on a B12 supplement. Less than 2 weeks later, the pins and needles were gone.

Now I'm taking it again as my glucose levels went up (to 112 mg/dL), but with the B12 supplement, and I plan to measure my B12 in two months time.

Metformin in combination with some kind of statin to lower cholesterol is common as well. I have that combination, and another side effect is dumping syndrome which also lowers your bodies ability to absorb nutrients. I was not told ever to supplement with B12, but I already supplement with other multivitamins to offset what I lose by dumping.

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That’s because you barely absorb any B12 from supplements. They’re essentially useless. Unfortunately, most people will require B12 injections.

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Does he consume all co factors, which are basically all nutrients, for erythropoiesis?