Excessive Thirst and Urination
Category: symptoms
Excessive thirst (polydipsia) and excessive urination (polyuria) — often abbreviated PU/PD — are among the most common signs of systemic disease in dogs and cats. When a pet drinks noticeably more water than usual and produces larger volumes of urine, it typically indicates the body is unable to properly regulate fluid balance. PU/PD is not a disease itself but a symptom that warrants veterinary investigation.
## What Is Normal?
**Normal water intake:** Dogs typically drink 1 ounce (30 mL) per pound of body weight per day. Cats typically drink about 4 ounces per 5 pounds of body weight daily. Polydipsia is defined as water intake exceeding 100 mL/kg/day.
**Normal urine output:** Dogs produce approximately 20-40 mL/kg/day. Cats produce slightly less. Polyuria is defined as urine production exceeding 50 mL/kg/day.
Measuring actual water intake at home can help your veterinarian determine severity. Measure water placed in the bowl and subtract what remains after 24 hours.
## Common Causes
**Endocrine/Hormonal disorders:** Diabetes mellitus — insufficient insulin production or insulin resistance. One of the most common causes of PU/PD. Cushings disease (hyperadrenocorticism) — excessive cortisol production. Common in middle-aged to older dogs. Addisons disease (hypoadrenocorticism) — insufficient cortisol and aldosterone. Hyperthyroidism — extremely common in older cats (rare in dogs). Causes weight loss despite increased appetite. Diabetes insipidus — rare. The kidneys cannot concentrate urine properly.
**Kidney disease:** Chronic kidney disease (CKD) — very common in older cats. Kidneys lose ability to concentrate urine, leading to increased water loss. Acute kidney injury from toxins, infections, or urinary obstruction. Pyelonephritis (kidney infection).
**Liver disease:** Liver failure impairs the bodys ability to regulate water balance and toxin clearance.
**Urinary tract conditions:** Urinary tract infection (UTI) — may cause increased frequency rather than true polyuria. Pyometra (infected uterus) — life-threatening condition in unspayed females. Causes PU/PD plus vaginal discharge, lethargy, and fever.
**Medications:** Corticosteroids (prednisone) — a very common cause. Diuretics. Phenobarbital (seizure medication). Thyroid supplementation.
**Other:** Hypercalcemia (elevated calcium — can indicate cancer). Polycythemia. Psychogenic polydipsia (behavioral — diagnosis of exclusion). Post-obstructive diuresis (after relief of urinary blockage).
## When to Seek Veterinary Care
Schedule a veterinary appointment if your pet is drinking noticeably more water than usual, needs to go outside more frequently or is having accidents, the litter box is wetter or heavier than usual, water bowls are emptying faster than normal, drinking is accompanied by weight loss, vomiting, or lethargy, or if your pet is an unspayed female showing any signs of illness (pyometra risk).
**Emergency situations:** Seek immediate care if your pet is also vomiting, lethargic, not eating, very weak, or if an unspayed female shows vaginal discharge — pyometra is a surgical emergency.
## Diagnosis
Your veterinarian will likely recommend a complete blood count (CBC), blood chemistry panel (kidney values, liver values, glucose, calcium, electrolytes), urinalysis with specific gravity (measures urine concentration), urine culture if infection is suspected, thyroid testing (T4, especially in older cats), cortisol testing if Cushings disease is suspected (ACTH stimulation or low-dose dexamethasone suppression test), abdominal ultrasound, and blood pressure measurement.
## Treatment
Treatment is directed at the underlying cause. Diabetes mellitus requires insulin therapy (injections) and dietary management. Kidney disease is managed with prescription diets, fluid therapy, and supportive medications. Cushings disease may require medication (trilostane or mitotane) or surgery. Hyperthyroidism in cats is treated with medication (methimazole), radioactive iodine therapy, surgery, or prescription diet. Pyometra requires emergency spay surgery.
## What You Can Do at Home
Never restrict water access in a pet with PU/PD — this can cause dangerous dehydration. Monitor and record daily water intake. Note any other symptoms (weight changes, appetite changes, lethargy). Collect a urine sample for your vet if possible (use a clean container). Schedule a veterinary appointment promptly.
## What Is Normal?
**Normal water intake:** Dogs typically drink 1 ounce (30 mL) per pound of body weight per day. Cats typically drink about 4 ounces per 5 pounds of body weight daily. Polydipsia is defined as water intake exceeding 100 mL/kg/day.
**Normal urine output:** Dogs produce approximately 20-40 mL/kg/day. Cats produce slightly less. Polyuria is defined as urine production exceeding 50 mL/kg/day.
Measuring actual water intake at home can help your veterinarian determine severity. Measure water placed in the bowl and subtract what remains after 24 hours.
## Common Causes
**Endocrine/Hormonal disorders:** Diabetes mellitus — insufficient insulin production or insulin resistance. One of the most common causes of PU/PD. Cushings disease (hyperadrenocorticism) — excessive cortisol production. Common in middle-aged to older dogs. Addisons disease (hypoadrenocorticism) — insufficient cortisol and aldosterone. Hyperthyroidism — extremely common in older cats (rare in dogs). Causes weight loss despite increased appetite. Diabetes insipidus — rare. The kidneys cannot concentrate urine properly.
**Kidney disease:** Chronic kidney disease (CKD) — very common in older cats. Kidneys lose ability to concentrate urine, leading to increased water loss. Acute kidney injury from toxins, infections, or urinary obstruction. Pyelonephritis (kidney infection).
**Liver disease:** Liver failure impairs the bodys ability to regulate water balance and toxin clearance.
**Urinary tract conditions:** Urinary tract infection (UTI) — may cause increased frequency rather than true polyuria. Pyometra (infected uterus) — life-threatening condition in unspayed females. Causes PU/PD plus vaginal discharge, lethargy, and fever.
**Medications:** Corticosteroids (prednisone) — a very common cause. Diuretics. Phenobarbital (seizure medication). Thyroid supplementation.
**Other:** Hypercalcemia (elevated calcium — can indicate cancer). Polycythemia. Psychogenic polydipsia (behavioral — diagnosis of exclusion). Post-obstructive diuresis (after relief of urinary blockage).
## When to Seek Veterinary Care
Schedule a veterinary appointment if your pet is drinking noticeably more water than usual, needs to go outside more frequently or is having accidents, the litter box is wetter or heavier than usual, water bowls are emptying faster than normal, drinking is accompanied by weight loss, vomiting, or lethargy, or if your pet is an unspayed female showing any signs of illness (pyometra risk).
**Emergency situations:** Seek immediate care if your pet is also vomiting, lethargic, not eating, very weak, or if an unspayed female shows vaginal discharge — pyometra is a surgical emergency.
## Diagnosis
Your veterinarian will likely recommend a complete blood count (CBC), blood chemistry panel (kidney values, liver values, glucose, calcium, electrolytes), urinalysis with specific gravity (measures urine concentration), urine culture if infection is suspected, thyroid testing (T4, especially in older cats), cortisol testing if Cushings disease is suspected (ACTH stimulation or low-dose dexamethasone suppression test), abdominal ultrasound, and blood pressure measurement.
## Treatment
Treatment is directed at the underlying cause. Diabetes mellitus requires insulin therapy (injections) and dietary management. Kidney disease is managed with prescription diets, fluid therapy, and supportive medications. Cushings disease may require medication (trilostane or mitotane) or surgery. Hyperthyroidism in cats is treated with medication (methimazole), radioactive iodine therapy, surgery, or prescription diet. Pyometra requires emergency spay surgery.
## What You Can Do at Home
Never restrict water access in a pet with PU/PD — this can cause dangerous dehydration. Monitor and record daily water intake. Note any other symptoms (weight changes, appetite changes, lethargy). Collect a urine sample for your vet if possible (use a clean container). Schedule a veterinary appointment promptly.
Source: Merck Veterinary Manual; AAHA Diabetes Management Guidelines; ISFM Consensus Guidelines on CKD