Metformin is a drug which has been widely used in clinical practice. Multiple clinical trials have suggested that long-term use of metformin could result in serum vitamin B12 reduction even deficiency. while vitamin B12 deficiency might lead to peripheral neuropathy. megaloblastic anemia and aggravation of preexisting cardiovascular diseases in diabetic patients. https://www.roneverhart.com/MagnaFlow-2001-2005-Honda-Civic-Street-Series-Cat-Back-Performance-Exhaust-System/