Blood uric acid is the concentration level of uric acid in the peripheral blood, and a blood uric acid of 421 μmol/L is usually abnormal. Uric acid is the end product of purine metabolism, mainly produced by the cell metabolic breakdown of nucleic acids and other purine-like compounds and purines in food by the action of enzymes. The saturation concentration of uric acid in the body at 37℃ is about 420µmol/L. Above this concentration, urate forms crystals and deposits in a variety of tissues, including the kidneys and synovial membranes of joints, causing tissue damage. Currently, blood uric acid >420µmol/L is clinically defined as hyperuricemia. Therefore, a blood uric acid of 421 µmol/L is usually abnormal. Higher values are usually considered to be related to alcoholism, high purine diet, medications, kidney damage and other causes. When uric acid is elevated, it is recommended to go to the rheumatology and immunology department, endocrinology department and other related departments of regular hospitals, and take medication as prescribed by the doctor if necessary.