Urine formation is an important physiological process through which the kidneys remove metabolic wastes and excess substances from the blood while maintaining the internal balance of water, electrolytes and acid–base status. In the context of yoga, proper kidney function is associated with the maintenance of a healthy body and efficient elimination of wastes. The formation of urine mainly takes place in the functional units of the kidneys called nephrons. Each kidney contains about one million nephrons. A nephron consists mainly of the glomerulus, Bowman’s capsule, proximal convoluted tubule, loop of Henle, distal convoluted tubule and collecting duct. Urine formation occurs through three major processes: glomerular filtration, tubular reabsorption and tubular secretion. Glomerular filtration is the first step. Blood enters the glomerulus through the afferent arteriole under relatively high pressure. The glomerulus is a network of capillaries surrounded by Bowman’s capsule. Because of the pressure, water and small dissolved substances such as glucose, amino acids, salts, urea and other waste products pass from the blood into Bowman’s capsule. Large plasma proteins and blood cells normally remain in the blood because they cannot pass through the filtration barrier. The fluid formed is called glomerular filtrate. Approximately 180 litres of filtrate may be produced each day in