SYMPTOM
Increased thirst and urination
Owners may observe increased thirst and urination in their pet.
Various conditions
This symptom can occur in multiple conditions and warrants further assessment.
Diabetes Mellitus
Insufficient insulin activity leaves glucose unable to enter cells, so blood glucose rises until it spills into the urine, drawing water out with it by osmotic effect. The resulting fluid loss triggers compensatory thirst. Middle-aged and older dogs, and certain breeds such as Miniature Schnauzers and Border Terriers, are recognised as more prone to developing this condition.
Hyperadrenocorticism (Cushing's Disease)
Chronically elevated cortisol, whether from a pituitary or adrenal source, interferes with the kidneys' ability to concentrate urine and increases thirst directly. Affected dogs, typically middle-aged to older, often also show a pot-bellied appearance, thinning coat, and increased appetite. Poodles, Dachshunds, and Boxers appear over-represented.
Chronic Kidney Disease
As functioning kidney tissue is gradually lost, the remaining nephrons lose their ability to concentrate urine, so more water is excreted and thirst rises to compensate. This is typically a slow, progressive process most often recognised in older dogs, though breed-related kidney conditions can produce it earlier in life. Weight loss and reduced appetite frequently develop alongside the drinking changes.
Hypercalcaemia of Malignancy
Certain tumours, including anal sac adenocarcinoma and multiple myeloma, release substances that raise blood calcium to levels which blunt the kidneys' response to antidiuretic hormone. This produces a dilute, high-volume urine output with matching increased thirst, sometimes before other signs of the underlying tumour become apparent. It is seen more often in middle-aged and older dogs.
Primary (Behavioural) Polydipsia
Some dogs drink more than physiologically needed for reasons unrelated to disease, including habit, boredom, a change to a drier diet, or simply warm weather and increased activity. This benign pattern produces normally dilute urine and no other signs of illness, and typically settles once the underlying trigger, such as diet or environment, is addressed.
Why timing matters
Early observation
Early recognition allows prompt assessment and intervention if needed.
Later presentation
Persistent or worsening signs may indicate progression requiring attention.
The significance of this symptom depends on its context, duration, and associated findings.
Conditions commonly associated
Leptospirosis
Kidney damage affects concentrating ability, leading to changes in water consumption and urination patterns.
Diabetes Mellitus in Dogs
In diabetes mellitus, the body cannot move glucose from the bloodstream into cells effectively, causing blood glucose to rise. The kidneys respond by filtering excess glucose into the urine, drawing water with it and prompting the dog to urinate more frequently and drink more to compensate for the fluid loss.
Diabetes Mellitus in Cats
Diabetes mellitus in cats causes elevated blood glucose that exceeds the kidney's capacity to reabsorb it, leading to glucose spillage into the urine. This osmotic effect draws water into the urine, increasing urination volume and triggering compensatory thirst.
Cushings Disease in Dogs
Excess cortisol in Cushing's disease interferes with antidiuretic hormone, reducing the kidney's ability to concentrate urine. This causes large volumes of dilute urine to be produced, and affected dogs typically drink substantially more water to maintain hydration.
Chronic Kidney Disease in Dogs
As kidney function declines in chronic kidney disease, the kidneys lose their ability to concentrate urine efficiently, producing larger volumes of dilute urine. Dogs compensate by drinking more water, and this pattern of increased thirst and urination often develops gradually over months.
Chronic Kidney Disease in Cats
Chronic kidney disease in cats impairs the kidneys' concentrating ability, causing them to produce more dilute urine in larger volumes. Affected cats tend to drink more to offset the fluid loss, though this compensation may not always keep pace with progressive disease.
Anal Sac Adenocarcinoma
Anal sac tumours can release a hormone-like substance that raises blood calcium, which in turn increases thirst and urine output.
Multiple Myeloma
Abnormal protein production and calcium disturbance associated with this bone marrow cancer can affect kidney function, increasing both thirst and urination.
Pituitary Macroadenoma
When the tumour is hormonally active, excess ACTH drives cortisol production and the classic increase in drinking and urinating.
Acromegaly in Cats
Acromegaly commonly drives insulin-resistant diabetes, so increased thirst and urination often appear alongside the underlying hormonal changes.
Ethylene Glycol Toxicity
In the early stages of poisoning, ethylene glycol increases urine output and drives a corresponding rise in thirst.
Glomerulonephritis
As protein leaks from the damaged kidney filters, the kidneys' concentrating ability falters and both thirst and urine output rise.
Hyperparathyroidism in Dogs
Increased thirst and urination reflect the kidneys' response to the persistently high blood calcium this condition produces.
Lyme Nephritis
Increased drinking and urination develop as the inflamed, protein-leaking kidneys lose their ability to conserve water.
Acute Kidney Injury
When the kidneys lose their ability to concentrate urine, the body produces larger volumes of dilute urine, which in turn drives increased thirst to compensate for the fluid being lost.
When to explore further
When the symptom is persistent or worsening
When other signs are present alongside
When daily activities or quality of life are affected
When there is uncertainty about the cause
Noting when this symptom occurs, any triggers, and how it changes over time can provide useful information for veterinary discussions.
Last reviewed: 24 April 2026 · Dr Alastair Greenway MRCVS