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.