Erythrocyte sedimentation rate is an important laboratory test in hematology. Inclusion body is an abnormal addition within red blood cell that can occur in cases of many abnormalities. Inclusion body is an object and has mass therefore, it poses its specific weight which can modify the normal sedimentation of red blood cell. Here, the author proposed the mechanism that reduce the erythrocyte sedimentation rate in splenectomized thalassemia and further imply for other conditions with inclusion body in red blood cell. It can demonstrate that the increase of additional mass due to inclusion body can reduce the time for sedimentation.