The normal value for urine red blood cells is no greater than 3 per high-powered field of view, and this is generally within the normal range. If a patient has a mild elevation of red blood cells or significant hematuria in the naked eye, a systematic investigation should be conducted. Common causes include kidney disease, or kidney damage caused by internal diseases, such as hypertension, diabetes mellitus, or rheumatic immune diseases. For example, there is lupus nephritis, which can lead to elevated red blood cells. Then there are some tumors or malformations, stones and other aspects that can also have elevated red blood cells. However, when elevated erythrocytes are found in such cases, morphological analysis of erythrocytes by phase contrast microscopy should be performed to clarify the proportion of malformed erythrocytes and determine whether the erythrocytes originate from the kidney or from epithelial exudation from the urinary system.