Dogs and cats can develop increased thirst (polydipsia) and urination (polyuria) secondary to numerous causes. This combination of polydipsia and polyuria is often abbreviated “PU/PD.” When possible, it can be very helpful to quantify the amount of water your dog or cat is drinking, to better determine if it’s excessive.
Dogs and cats are considered polydipsic (drinking too much water) if they’re drinking more than 100mL of water per kilogram of body weight per day. For example, a dog that weighs 30 kilograms should not drink more than 3 liters of water per day. It can be more difficult to quantify urination, but it’s important to differentiate frequent urination from large volume urinations. Frequent small volumes of urination are often associated with urinary tract diseases, while very large volume urinations may be due to metabolic and endocrine diseases, organ dysfunction, or certain serious infections.
Some diseases cause increased urination first; increased urine production necessitates increased water intake in order to maintain normal hydration. Other diseases cause increased drinking first, which in turn leads to increased urine production.
In dogs, common causes of PU/PD include hyperadrenocorticism (Cushing’s disease), diabetes mellitus (high blood sugar), and kidney disease. Other causes include high calcium, liver dysfunction or failure, Addison’s disease, diabetes insipidus, pyometra (uterine infection), and psychogenic polydipsia. Psychogenic polydipsia is a condition in which pets drink excessively for no underlying reason (behavioral). This is a diagnosis of exclusion, after all other causes of PU/PD are ruled-out.
In cats, common causes of increased drinking and urination include kidney disease, diabetes mellitus (high blood sugar), and hyperthyroidism. Other causes are similar to those listed for dogs.
Any pet exhibiting increased thirst and urination should be further evaluated; additional testing including blood work and urine testing, as well as more specific tests as indicated, will likely be performed. Treatment of PU/PD requires treatment of the underlying disease process is often necessary. Importantly, you should never restrict your pet’s access to water, as this could lead to life-threatening complications.