The kidneys filter blood and remove waste from the body. They regulate fluid and electrolyte balance and blood pressure. Each kidney is about the size of a fist and can filter about 5 liters of blood per day. There are over 1 million nephrons in each kidney that together would form a chain over 100 km long. High blood pressure, diabetes, infections, kidney stones, and accidents can lead to kidney failure if not properly managed. Prevention through lifestyle changes like drinking water, controlling blood pressure and diabetes, and avoiding overuse of drugs can help reduce the risk of kidney failure.