Mixed red blood cells do not necessarily mean nephritis. Mixed erythrocytes refers to the presence of a mixture of aberrant and normal red blood cells in the urine. If the red blood cells are increased due to nephritis, then a high percentage of aberrant red blood cells, usually above 80%, will be found when performing an erythrocyte microscopy; if the hematuria is caused by non-renal factors, then the percentage of aberrant red blood cells will be less, below 80%. If it is mixed red blood cells, then this time suggests that there may be renal factors involved as well as other factors, such as kidney stones, urinary tract infections, etc. Therefore, when mixed red blood cells are found in the urine, it is important to actively look for other causes and rule out secondary nephritis. It is only after treatment and observation that we can rule out nephritis as the cause.