💧 Vet Guide 2025: Polyuria & Polydipsia in Dogs and Cats – Causes, Diagnosis & Management 🐶🐱🧪

By Dr Duncan Houston, BVSc

🔍 What Is PU/PD?

Polyuria (PU) means excessive urination, and polydipsia (PD) means excessive thirst. The two often occur together. As the body loses more water through urine, it signals thirst to prevent dehydration. These symptoms are often a of an underlying condition. 💧

📉 How the Body Controls Water

Hydration is regulated by multiple systems, including:

• 🧠 The brain’s thirst center
• 🩸 Blood pressure sensors
• 💉 Anti-diuretic hormone (ADH)
• 🧪 Kidney filtration function

When kidneys stop concentrating urine due to damage or disease, the body tries to flush toxins out with increased urine—and responds by increasing water intake. If ADH is lacking or ignored by the kidneys, the result is the same: PU/PD.

🐾 Common Causes of PU/PD in Dogs

• 🐕 Chronic Kidney Disease (CKD)
• 🧬 Cushing’s Disease (Hyperadrenocorticism)
• 🍬 Diabetes Mellitus
• 💊 Glucocorticoid or diuretic use
• 🧫 Pyometra (uterine infection in females)

🐱 Common Causes of PU/PD in Cats

• 🐱 Chronic Kidney Disease (CKD)
• 🍬 Diabetes Mellitus
• 🔥 Hyperthyroidism
• 🧬 Liver disease

Rare Causes in Both Dogs and Cats

• 🧬 Diabetes insipidus (not related to blood sugar)
• 🦠 Leptospirosis
• 🧠 Hypothalamic or pituitary disorders
• 🧫 Cancer or adrenal gland abnormalities

🧪 Diagnosing PU/PD

Step 1: Physical Exam & History

Your vet will ask about:

• 📅 Changes in drinking/urination
• 🐾 Appetite or weight changes
• 💊 Current medications

Step 2: Lab Testing

• 🧪 Urinalysis: Measures concentration (USG), infection, and glucose
• 🧫 Urine culture: Detects bacterial infections
• 💉 Blood work: CBC, chemistry panel, glucose, kidney/liver function
• 🧪 Endocrine tests: Cushing’s, Addison’s, thyroid

Low USG (specific gravity) with high urine volume suggests impaired kidney concentration. Normal blood sugar rules out diabetes. 🧬

Step 3: Imaging

• 🩻 X-rays or ultrasound to assess kidneys, bladder, adrenal glands
• 🔬 May be needed to rule out tumors or pyometra

⚠️ Important Note on Diabetes Insipidus

This rare condition causes extreme PU/PD due to ADH malfunction—not to be confused with diabetes mellitus. Special water deprivation testing and imaging are needed to confirm. 🧠💧

💊 Treatment Depends on the Cause

Examples:

• 🍬 Diabetes Mellitus: Insulin therapy, diet change
• 💊 Cushing’s: Hormone-suppressing medications
• 🐾 CKD: Renal diet, subcutaneous fluids, blood pressure meds
• 🧬 Hyperthyroidism (in cats): Medication or radioactive iodine therapy

Once the primary issue is controlled, thirst and urination typically return to normal.

📋 Monitoring Tips at Home

• 📏 Measure daily water intake if possible
• 🕵️ Look for urinary accidents, damp bedding
• 📊 Note weight, energy, and appetite changes

Normal daily water intake is ~50–60 ml per kg of body weight. Excess indicates PU/PD. 🧪

🩺 Final Thoughts from Dr Duncan Houston

PU/PD in dogs and cats isn’t a disease—it’s a symptom. But it’s often the first and most obvious sign that something isn’t right. With proper testing and targeted treatment, most causes can be managed effectively. The key is catching the issue early and working closely with your vet. 🐾💧

📲 Noticed Excessive Drinking or Urination? Ask A Vet Today

Don’t wait—early diagnosis is essential. Download the Ask A Vet app and chat live with Dr Duncan Houston or other licensed vets for answers, lab review, and treatment guidance 🐶🐱💬