Renal failure is the condition in which the kidneys can no longer perform their essential work of filtering waste, balancing fluids and electrolytes, and regulating blood pressure. Acute renal failure strikes suddenly, often after severe dehydration, infection, or toxin exposure, and may be reversible with prompt treatment. Chronic renal failure develops over years, most commonly from diabetes and hypertension, progressing until dialysis or transplantation becomes necessary. Nutrition management is demanding: protein, sodium, potassium, phosphorus, and fluid all need careful control, adjusted to the stage of disease and the type of dialysis. Infections and the formation of kidney stones can both complicate the picture. Early detection through blood and urine tests offers the best chance of slowing the decline.