the medical term for excessive thirst or craving large amounts of liquid is
Polydipsia Polydipsia is excessive thirst or excess drinking.[1] The word derives from the Greek πολυδίψιος (poludípsios) "very thirsty",[2] which is derived from πολύς (polús, "much, many") + δίψα (dípsa, "thirst"). Polydipsia is a nonspecific symptom in various medical disorders. It also occurs as an abnormal behaviour in some non-human animals, such as in birds.[3]