Thirst is the feeling of needing to drink something. It occurs whenever the body is dehydrated for any reason. Any condition that can result in a loss of body water can lead to thirst or excessive thirst. For this reason, thirst is a characteristic symptoms of certain medical conditions, most notably diabetes mellitus. Thirst may be accompanied by other signs of dehydration such as decreased urine output, reduced sweating and tear production, muscle cramps, weakness, lightheadedness, and nausea. Dehydration and thirst may be minor or severe, depending upon the amount of water lost by the body. Polydipsia is the medical term that refers to increased or excessive thirst.