I have been on metformin for about 14years. Started with 500mg twice a day. but had been taking 1000mg twice a day this too for about more than 10years. I am worried about vitamin deficiencies associated with that. I am on LCHF now for about 10 months. I get very tired . I have read Long term use of metformin can cause low Vit. B12 and D . All the advice welcome.