Methylcobalamin is an endogenous vitamin B12, which is a water-soluble vitamin and can be excreted with the body’s metabolic system in daily life, so there is no time limit of how many months methylcobalamin can be taken at most. However, it should be noted that if there is still no obvious effect after taking it for more than 1 month, it is necessary to stop taking methylcobalamin and consult a doctor, and be guided by the doctor to replace other drugs for treatment. Methylcobalamin is a vitamin B12, which is involved in the synthesis of nerve myelin in the body. If there is a deficiency of this vitamin in the body, there will be an impairment in the production of nerve myelin, which will cause peripheral neuropathy and lead to diseases such as dementia and hyperhomocysteinemia. Vitamin B12 is also involved in carbon cycling and homocysteine degradation in the body, so for conditions such as diabetic peripheral neuropathy, alcoholic peripheral neuropathy, and nerve damage due to carpal tunnel syndrome, methylcobalamin can be taken orally under medical supervision. If the patient is not paranoid, he can also choose to consume some foods containing vitamin B12 for conditioning, such as meat and pork liver, which are rich in vitamin stored in these foods and can meet normal needs. However, if the patient is a partial eater or a vegetarian, he can be treated by oral supplementation of methylcobalamin. If, in combination with improved dietary habits, the problem of partiality is changed so that malnutrition improves and the symptoms caused by nerve damage disappear, discontinuation of the drug can be considered. However, in the case of patients with subacute joint degeneration, patients with methylcobalamin deficiency due to endogenous factor deficiency must be supplemented by injection for life.