The primary function of human kidneys is to filter waste products and excess substances from the blood to produce urine. This vital process helps maintain the body's fluid and electrolyte balance, regulating levels of minerals like sodium, potassium, and calcium. The kidneys also play a role in blood pressure regulation and the production of hormones that influence red blood cell production and calcium metabolism. Each kidney contains millions of nephrons, which are the functional units responsible for this filtration process. Proper kidney function is essential for overall health, and any impairment can lead to serious medical issues.