metformin side effects long term
(B12 and Metformin Nerve Damage) How does a drug like Metformin that has so many benefits cause such a severe side effect as nerve damage? Three out of 10 people who take metformin long-term develop a deficiency of vitamin B12. It can take 10 or 15 years to develop symptoms of B12 deficiency since the liver stores B12 - and it can take that long to deplete those stores. B12 deficiency causes damage to nerves that may be irreversible.