Diabetes Insipidus in Cats: Symptoms, Diagnosis & Treatment (2026)

Central DI — causes of ADH deficiency in cats

• •Idiopathic (most common): No identifiable cause found on full workup. The hypothalamus or pituitary stops producing enough ADH without any detectable tumor, trauma, or systemic disease. This form responds well to DDAVP.
• •Head trauma: Damage to the pituitary stalk or hypothalamus from falls, vehicular injury, or blunt trauma. DI can appear days to weeks after the traumatic event and may be temporary or permanent.
• •Pituitary or hypothalamic tumor: A pituitary mass (such as a craniopharyngioma or pituitary adenoma) compressing or destroying ADH-producing cells. These cats may also show neurological signs. Note: acromegaly (caused by a GH-secreting pituitary tumor) is a distinct condition that more often causes insulin-resistant diabetes mellitus.
• •Post-surgical: Following procedures near the pituitary or hypothalamus; sometimes transient, sometimes permanent.
• •Congenital: Rare; kittens present with PU/PD from an early age.

Nephrogenic DI — causes of kidney unresponsiveness in cats

• •Hypercalcemia: One of the more common causes of acquired NDI in cats; elevated calcium directly impairs ADH signaling in the tubules. Causes include primary hyperparathyroidism, hypervitaminosis D, idiopathic hypercalcemia, and certain cancers.
• •Pyometra or uterine infection: Bacterial toxins from reproductive tract infection interfere with renal ADH response. Resolves after spay in intact females.
• •Chronic kidney disease: Loss of renal medullary concentrating ability is part of CKD — though other markers (azotemia, small kidneys) are typically present and the full diagnosis is usually CKD rather than "pure" NDI.
• •Hypokalemia: Low potassium impairs renal concentrating mechanisms.
• •Congenital NDI: Extremely rare in cats; present from kittenhood.

Step 1: Urinalysis — the starting point

Urine specific gravity (USG) is the cornerstone finding. In DI, USG is persistently very low — 1.001 to 1.006, sometimes up to 1.008. Normal cat urine is typically 1.035–1.060. Isosthenuria (1.008–1.012) suggests reduced concentrating ability from kidney disease. Crucially, there is no glucose in the urine — glucosuria immediately makes diabetes mellitus far more likely. The urine sediment is typically bland and unremarkable.

Step 2: Bloodwork — ruling out common causes

A full chemistry panel, CBC, and T4 (thyroid level) are essential in any cat with PU/PD. Understanding how to read cat blood test results helps you follow what your vet is looking for at each step:

• •T4 rules out hyperthyroidism — the most common cause of PU/PD in middle-aged and older cats
• •Blood glucose and fructosamine rule out diabetes mellitus
• •BUN, creatinine, and SDMA assess kidney function
• •Calcium rules out hypercalcemia (a common acquired cause of NDI in cats)
• •Liver values assess hepatic disease
• •Potassium and sodium levels — sodium may be mildly elevated in DI

Step 3: Modified water deprivation test

Performed in hospital with close supervision. Water is withheld while urine specific gravity, body weight, urine osmolality, and clinical status are monitored at regular intervals. The test is stopped if the cat loses 5% of body weight, if USG rises above 1.030 (normal response), or if clinical concern arises.

Step 4: DDAVP trial (alternative or confirmatory approach)

In cats that are too unwell or unstable for a formal deprivation test, a DDAVP therapeutic trial may be used instead. The cat is given DDAVP drops for 5–7 days; if water intake normalizes and urine concentrates, central DI is supported. No response suggests nephrogenic DI.

Step 5: Brain imaging (if a structural cause is suspected)

If neurological signs are present, or if no obvious systemic cause of CDI is found, MRI of the brain is recommended to look for pituitary or hypothalamic masses. CT may be substituted if MRI is unavailable. Imaging findings guide both prognosis and treatment planning.

Central DI: Desmopressin (DDAVP)

Desmopressin acetate is a synthetic analog of ADH that replaces the missing hormone. In cats, it is given as drops placed into the conjunctival sac (inside the lower eyelid), most commonly 1–4 drops of the 0.01% solution 2–3 times daily. The eye mucosa absorbs the medication well, bypassing the poor oral bioavailability of the compound.

• •Conjunctival drops: Most common route; typically well tolerated with gentle restraint
• •Intranasal drops: Applied to the nasal mucosa; some cats tolerate this better than eye drops
• •Oral tablets: Available but require much higher doses due to low absorption; more expensive
• •Injectable: Used in hospital or when other routes fail

Most cats respond rapidly — urine concentration improves and water intake drops noticeably within hours to a few days of beginning DDAVP. Dose is adjusted based on clinical response. The goal is to control symptoms, not to achieve a specific USG number.

Acquired Nephrogenic DI: Treat the underlying disease

These cats do not respond to DDAVP because their kidneys cannot respond to ADH regardless of how much is given. Treatment focuses on the root cause: correcting hypercalcemia, spaying a cat with pyometra, treating hyperthyroidism if it is contributing to concentrating defects, or discontinuing a causative medication. When the underlying problem resolves, renal concentrating ability often returns toward normal.

Congenital Nephrogenic DI: Thiazide diuretics and diet

Extremely rare in cats, but managed similarly to dogs with congenital NDI — thiazide diuretics (such as hydrochlorothiazide) create a mild volume-depleted state that shifts water reabsorption to the proximal tubule (which doesn't require ADH), reducing the volume of fluid that reaches the ADH-dependent collecting duct. A low-sodium diet enhances the effect. The result is a modest but meaningful reduction in urine output and thirst.

What is diabetes insipidus in cats?

Diabetes insipidus is a disorder of water regulation — not blood sugar. It occurs when the brain doesn't produce enough ADH (antidiuretic hormone), or when the kidneys can't respond to it. Without functional ADH signaling, the kidneys excrete enormous volumes of dilute urine. Cats compensate by drinking far more water. Blood glucose is completely normal — this is an entirely different disease from diabetes mellitus.

How do I know if my cat has diabetes insipidus vs. hyperthyroidism or kidney disease?

All three can cause excessive thirst and urination. Your vet will run a T4 test (for hyperthyroidism), blood glucose and fructosamine (for diabetes mellitus), and kidney function tests (BUN, creatinine, SDMA) alongside a urinalysis. In DI, all these are normal while the urine is consistently extremely dilute (SG 1.001–1.006) with no glucose. The water deprivation test is the key test that differentiates DI from primary polydipsia and distinguishes central from nephrogenic DI.

Is diabetes insipidus painful for cats?

Uncomplicated DI itself is not painful. However, if a cat with DI is ever deprived of water — even briefly — dangerous dehydration and hypernatremia can develop rapidly, causing neurological symptoms and real distress. With consistent treatment and water access, cats with DI are comfortable. If there is a pituitary tumor causing the DI, the tumor itself may eventually cause other symptoms.

How is DDAVP given to cats?

In cats, desmopressin (DDAVP) is most commonly given as drops placed inside the lower eyelid (conjunctival sac) using a small dropper — typically 1–4 drops of the 0.01% solution, 2–3 times daily. Some cats receive it as intranasal drops instead. Oral tablets are also available but require higher doses due to poor absorption and are more expensive. Most cats tolerate the eye drop route well after some initial adjustment.

Can a cat with diabetes insipidus live a normal life?

Yes — cats with central DI typically respond very well to DDAVP and maintain an excellent quality of life. They need water always available and consistent medication, but otherwise their daily life is unchanged. The main challenge is ensuring every caregiver (pet sitter, boarding facility, vet clinic) understands that continuous water access is medically critical.

Is diabetes insipidus common in cats?

No — DI is rare in cats. Most cats presenting with excessive thirst and urination have hyperthyroidism, diabetes mellitus, or chronic kidney disease. DI is worked up when routine testing rules out these common conditions and urine remains consistently extremely dilute. When DI is confirmed, central DI is more common than nephrogenic DI in cats, and idiopathic central DI is the most frequent specific diagnosis.