Final answer:
Hemodialysis is performed on patients with kidney failure, and it requires frequent treatments to remove waste products and excess water from the bloodstream. Regular testing is necessary during hemodialysis to monitor patients' condition and ensure effective treatment.
Step-by-step explanation:
Hemodialysis is typically performed on patients with kidney failure, and it involves filtering the blood externally through a machine. The procedure is usually done 3 to 4 times a week for a few hours each time. The frequent treatments are necessary because waste products and excess water constantly build up in the bloodstream due to the kidneys' inability to filter them out. Therefore, regular testing should take place when patients are receiving hemodialysis to monitor their condition and ensure effective treatment.