Diabetes insipidus is the inability of the kidneys to respond to vasopressin. Vasopressin is released in response to a fall in the water content of blood plasma and leads to an increase in the permeability to water of the distal and collecting tubules of the nephron in the kidney. As a result of which the reabsorption of water from the glomerular filtrate is increased. Diabetes insipidus is characterised by micturating dilute urine several times a day.