The three main signs of diabetes mellitus are known as the diabetic triad: polyuria, polydipsia and polyphagia. Polyuria is the excessive elimination of urine; in diabetes it is caused by reduced water resorption in the renal tubules due to increased osmolarity of the glomerular filtrate (caused by excessive glucose). Polydipsia is the exaggerated ingestion of water; the thirst is due to the excessive water loss in the urine. Polyphagia is the exaggerated ingestion of food caused by deficiency in energy generation by glucose-lacking cells.