When hematuria occurs after fever, the first step is to clarify whether the patient has urinary tract infections such as frequent, urgent and painful urination. If the hematuria is caused by urinary tract infection, the presence of pyelonephritis or cystitis should be considered; if the hematuria is caused by fever or diarrhea, the possibility of IgA nephropathy should be excluded; IgA nephropathy is usually caused by mucosal damage, which can lead to hematuria in the naked eye, usually after 24 hours or within a few days, and patients should be treated early to prevent further aggravation of the disease. If the patient’s body temperature rises above 38.5℃ after infection, he/she should pay high attention and seek medical attention in time to check the patient’s blood and urine routine, except for urinary tract infection. If the patient is not urinary tract infection, it should be highly suspected that it is a disease of the kidney itself, of which IgA nephropathy is more likely.