Polydipsia

Lore & Background

Polydipsia is a nonspecific symptom that can be an initial sign of diabetes mellitus, especially in poorly controlled cases or when patient adherence to medication is low. It also occurs in diabetes insipidus, a condition distinct from diabetes mellitus. Other physiological causes include changes in extracellular fluid osmolality, hypokalemia, decreased blood volume from major hemorrhage, and osmotic diuresis. Anticholinergic poisoning can also produce polydipsia, while zinc deficiency may contribute because zinc helps the body absorb fluids and retain sodium.

Reader's Guide

Primary polydipsia describes excessive thirst and water intake without physiological stimuli. This includes psychogenic polydipsia, seen in patients with mental illnesses such as schizophrenia or developmental disabilities, which can be life-threatening if water intake exceeds kidney excretion, diluting serum sodium and risking seizures or cardiac arrest. A milder form, habit polydipsia, occurs in the absence of psychosis. Habit drinking is the most common imitator of diabetes insipidus, and the distinction is made via a water deprivation test, though a psychiatric consult may be considered first. Polydipsia is a symptom, not a disease, and is often accompanied by polyuria and low sodium levels. Diagnosis may involve tests for diabetes insipidus and diabetes mellitus, as well as blood serum tests for osmolality, red blood cell concentration, BUN, and sodium.

Did You Know?

• The word polydipsia derives from Ancient Greek πολύς (polús) 'much, many' and δίψα (dípsa) 'thirst'.
• Polydipsia occurs as an abnormal behavior in some non-human animals, such as birds.
• Psychogenic polydipsia can be life-threatening because excessive water intake dilutes serum sodium, potentially causing seizures and cardiac arrest.
• Zinc deficiency can be a possible cause of polydipsia, as zinc helps the body absorb fluids and retain sodium.