Diabetes insipidus (DI) is a metabolic disorder in which dogs demonstrate a severe overproduction of urine. The most common form of DI is called central DI, and is due to insufficient production of anti-diuretic hormone (ADH), a hormone responsible for concentrating the urine into a small volume. Dogs with DI urinate and drink excessively.

Most cases of central DI are idiopathic, meaning that they occur for no known reason; however, damage to the part of the brain that makes ADH can lead to DI. Cancer or trauma are two common known causes of central DI. A second uncommon form called nephrogenic DI results from impaired responsiveness of the kidney to the action of ADH. It is a rare, congenital condition and has occasionally been reported to be hereditary in a few instances.

Excessive urination and thirst is a common clinical sign. The diagnostic tests recommended will help differentiate DI from these other conditions that can cause excessive thirst and urination:

Diabetes mellitus (excessive sugar in the blood)

Renal glycosuria (excessive sugar in the urine, but not diabetic)

Chronic kidney failure

Pyometra (infection of the uterus)

Hypercalcemia, a condition of excessively high calcium levels in the blood

Liver failure

Hyperadrenocorticism, also called Cushing's disease, a condition of overactive adrenal glands

Pyelonephritis, an infection of the kidneys

Hypokalemia (low potassium levels in the blood)

Hypoadrenocorticism, also called Addison's disease, a condition of underactive adrenal glands

Hyperthyroidism (excessive thyroid activity)

Acromegaly (excessive production of growth hormone)

Psychogenic polydipsia (excessive drinking due to psychological reasons, such as a change in the pet's environment