Hemodialysis Hemodialysis uses a special filter called a dialyzer as an artificial kidney to clean the blood of waste products and remove the extra fluid that accumulates. The dialysis machine pumps blood through the dialyzer. The cleaned blood flows out of the dialyzer and back into the bloodstream. Most people undergo three dialysis sessions each week, for four to five hours each time using their dialysis access. During dialysis, a person also receives medication to replace the hormones that the kidneys are unable to produce.