Due to any abnormality or malfunctioning of the kidneys, it may cause improper filtration and retention of urea in blood, resulting in a condition known as uremia. The normal level of urea in an adult is around 7 to 20 mg/dL of blood. In these uremic patients, a process known as hemodialysis is beneficial. In this process, the blood of a patient is drained by a convenient artery, and after adding anticoagulant like heparin, it is pumped into the dialysing unit which contains a coiled cellophane tube suspended in the dialysing fluid which have the same composition as that of plasma except for nitrogenous waste i.e., urea. As nitrogenous wastes are absent in dialysing fluid, these substances move out freely through the porous cellophane membrane based on concentration gradient. Thus, the blood gets filtered. This filtered blood after adding anti-heparin is pumped back to the body.