Table of Contents
What Is PU/PD?
PU/PD stands for polyuria (increased urine production) and polydipsia (increased thirst and water intake). The two are written together because they almost always travel together.
The pairing reflects a simple physiological loop: a patient that loses excess water in dilute urine becomes mildly dehydrated and drinks more to keep up, while a patient that drinks excessively must produce more urine to offload it. Because so many diseases can start that cycle, PU/PD is a high-yield clinical clue rather than a diagnosis in itself.
Normal vs. Increased Thresholds
Water intake (dogs)
Normal is generally under about 90–100 mL/kg/day; intake above roughly 100 mL/kg/day is considered polydipsia. Cats normally drink less, so their threshold is lower.
Urine output
Normal output is often cited at about 1–2 mL/kg/hour. Sustained output above roughly 2 mL/kg/hour (about 50 mL/kg/day) is considered polyuria.
These are general teaching values. Thresholds vary with diet, ambient temperature, and individual patient, so the trend over time and the wider clinical picture always outweigh a single measurement.
Common Differentials
The differential list for PU/PD is broad, which is why it usually triggers a systematic workup — history, physical exam, bloodwork, and urinalysis (including urine specific gravity). Common categories include:
1Renal
- • Chronic kidney disease — a leading cause in older dogs and cats
- • The kidneys lose the ability to concentrate urine effectively
2Endocrine
- • Diabetes mellitus (osmotic diuresis from glucosuria)
- • Hyperadrenocorticism / Cushing’s disease (common in dogs)
- • Hyperthyroidism (common in older cats)
- • Diabetes insipidus (central or nephrogenic)
3Metabolic & Electrolyte
- • Hypercalcemia
- • Hepatic disease / portosystemic shunt
- • Hypokalemia
4Other
- • Pyometra in intact females
- • Drug effects (glucocorticoids, diuretics)
- • Primary (psychogenic) polydipsia
Quantifying & Documenting
PU/PD usually surfaces first in the history when an owner mentions refilling the water bowl more often or larger urine clumps in the litter box. Whenever possible it helps to make it objective: asking the owner to measure total daily water intake and converting to mL/kg/day gives a baseline that can be tracked against urine specific gravity and the diagnostic plan. VetVisit AI captures those history details from the conversation and structures them in the note so the workup and follow-up are easy to follow visit over visit.
Frequently Asked Questions
What does PU/PD mean in veterinary medicine?
PU/PD stands for polyuria and polydipsia — increased urine production (polyuria) and increased water intake or thirst (polydipsia). The two almost always occur together, since a patient losing more water in the urine drinks more to compensate, and vice versa.
How much water intake is considered polydipsia in dogs?
In dogs, normal water intake is generally under roughly 90 to 100 mL/kg/day, and intake above about 100 mL/kg/day is typically considered polydipsia. Cats normally drink less, so their threshold is lower. These are general reference figures — trends and the overall clinical picture matter more than a single number.
What counts as polyuria?
Polyuria is urine production above the normal range — normal output is often cited at roughly 1 to 2 mL/kg/hour, so sustained output above about 2 mL/kg/hour (or roughly 50 mL/kg/day) is considered polyuria. In practice it is often recognized indirectly through dilute urine and increased water intake.
What are the most common causes of PU/PD in dogs and cats?
Common differentials include chronic kidney disease, diabetes mellitus, hyperadrenocorticism (Cushing’s) in dogs, hyperthyroidism in cats, diabetes insipidus, hypercalcemia, liver disease, pyometra in intact females, and certain drugs such as glucocorticoids and diuretics. The list is broad, so PU/PD usually prompts a systematic diagnostic workup.
How is PU/PD documented in the record?
PU/PD often first appears in the history (Subjective) when an owner reports the pet drinking or urinating more. When possible it is quantified — measuring daily water intake in mL/kg/day gives an objective baseline — and then followed alongside urine specific gravity and the diagnostic plan.
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Related Resources
Dehydration Assessment Guide
The flip side of water balance — estimating fluid deficit on physical exam.
IV Fluid Rate Calculator
Calculate maintenance and deficit fluid rates for the hospitalized patient.
IV Fluid Drip Rate Calculator
Convert a fluid rate in ml/hr into drops per minute for a gravity giving set.
TPR in Veterinary Medicine
Temperature, pulse, and respiration reference ranges by species.
Physical Exam Form
Systematic PE checklist to pair with the history when working up PU/PD.