What is the medical term for excessive or abnormal thirst?

The medical term for excessive or abnormal thirst is polydipsia.

Polydipsia describes unusually strong thirst or excessive drinking. It is a symptom rather than a disease itself, so clinicians look for the condition causing it. Diabetes mellitus is a well-known cause: elevated blood glucose can draw water into the urine, increasing urination and prompting the person to drink more.

Polydipsia can also occur with diabetes insipidus, dehydration, blood loss, low potassium, certain medications, or changes in the concentration of body fluids. When excessive drinking begins without a normal physiological trigger, it may be called primary polydipsia. Severe compulsive water intake can dilute the sodium concentration in blood and lead to dangerous hyponatremia.

Polydipsia is often mentioned alongside polyuria, which means excessive urination, but the terms are not interchangeable. Polyphagia means excessive hunger, while dysphagia means difficulty swallowing. The shared prefix poly- means “many” or “much,” but the rest of each word identifies a different symptom. Persistent excessive thirst warrants medical evaluation rather than simply increasing fluid intake.