HCY stands for homocysteine and is a blood test. Homocysteine, also known as homocysteine, is a four-carbon sulfur-containing amino acid in the same family as cysteine and is an important intermediate in the metabolism of methionine, which is not involved in protein synthesis in the body. Many factors such as genetics, renal insufficiency, hormones, drugs, nutrition, and even smoking may affect the metabolism of homocysteine in the body, resulting in hyperhomocysteinemia. It is now believed that hyperhomocysteinemia is closely related to the correlation between heart, brain, peripheral blood vessels, especially coronary heart disease, atherosclerosis and stroke, etc. It is necessary to check for homocysteine in case of heart disease, cerebrovascular disease, peripheral blood vessel disease or atherosclerosis.