Homocysteine 13 μmol/L is normal. Homocysteine is an important intermediate product in the metabolism of methionine and cysteine. The reference range of homocysteine in human plasma is 5-15 μmol/L, and greater than 15 μmol/L can be diagnosed as hyperhomocysteinemia. Homocysteine is mainly derived from daily diet, and irrational dietary structure is prone to hyperhomocysteinemia, which is a high-risk factor for atherosclerotic lesions. The current homocysteine level of 13 μmol/L is within the normal range, but patients with a history of coronary artery disease or stroke should pay close attention to avoid cardiovascular and cerebrovascular damage caused by progressive elevation of homocysteine. Patients diagnosed with hyperhomocysteinemia will not experience symptoms in the short term, but prolonged elevation of homocysteine is detrimental to cardiovascular and cerebrovascular health. It is recommended to take oral folic acid tablets, vitamin B6, vitamin B12 and other medications to lower homocysteine levels. If there is any discomfort, you should seek medical advice and follow the doctor’s instructions.