Methylcobalamin is only allowed to take one tablet per day may be to consider the patient’s age, all body functions, especially kidney function decline, considering the relatively slow metabolism of the drug to reduce the dose. Or after taking the drug appeared some slight discomfort symptoms (nausea, vomiting) and need to take the drug treatment patients, by reducing the dose to reduce the discomfort symptoms. Methylcobalamin is an endogenous vitamin B12, which mainly has a nutritive effect on nerves, and is indicated for peripheral neuropathy. The usual dose for adults is 0.5 mg (one tablet) three times daily. In the elderly, the body’s function decreases, the tolerance level of the drug will be reduced, and the decline of renal function will also lead to the prolongation of the drug’s retention in the body, so it is necessary to consider reducing the dosage. Patients who experience mild but not serious discomfort may consider reducing the dose and continuing to take the drug. If more serious discomfort occurs after taking the drug, you should stop taking the drug immediately and go to the hospital for prompt treatment.