Certified Nephrology Nurse Exam Practice 2025 – Complete Study Guide

The primary function of the kidneys is to filter waste products from the blood and excrete them in urine. This is a critical role in maintaining homeostasis within the body. The kidneys remove metabolic byproducts, toxins, and excess substances from the bloodstream, allowing for the regulation of body fluid and electrolyte balance. As blood passes through the kidneys, it is processed by nephrons, which filter out waste while reabsorbing necessary substances back into the bloodstream.

While the regulation of blood pressure and volume, production of hormones, and storage of excess water and nutrients are also vital functions associated with the kidneys, they are secondary to the fundamental function of waste filtration. The removal of waste is essential for preventing the accumulation of harmful substances in the body, which is the primary role the kidneys fulfill. Other functions, like hormone production (for example, erythropoietin and renin), support this primary function, but they do not replace it. The ability of the kidneys to filter blood is what ultimately contributes to overall health and homeostasis.