A condition in which the kidneys lose their ability to filter waste products, balance fluids and electrolytes, and regulate blood pressure effectively. Acute kidney failure develops suddenly, often from dehydration, infection, or toxins, and may be reversible with prompt treatment. Chronic kidney failure progresses over years, commonly driven by diabetes and hypertension, and is staged by declining filtration rate. Diet becomes a critical part of management: patients typically need controlled protein, sodium, potassium, and phosphorus intakes, with fluid restrictions in advanced stages. End-stage kidney failure requires dialysis or transplantation. Early detection through blood and urine tests allows interventions that can slow progression.