Hypercalciuria — excess calcium in rabbit urine — is so common in rabbits that a small amount of white-to-creamy urine sediment is normal. When it becomes excessive, calcium "sludge" accumulates in the bladder and can form gritty stones that obstruct outflow or damage the bladder wall. Knowing the difference between normal rabbit urine and a problem worth addressing can save your rabbit unnecessary pain.
Last reviewed: June 2026
What Is Hypercalciuria in Rabbits?
Rabbits have uniquely calcium-rich urine compared to all other common companion animals. Unlike dogs and cats, which regulate blood calcium through the gut and adjust urinary excretion minimally, rabbits absorb nearly all dietary calcium and excrete the excess through the kidneys — producing urine that is naturally cloudy with calcium carbonate crystals, as described in Quesenberry and Carpenter's Ferrets, Rabbits and Rodents.
Normal rabbit urine ranges from clear yellow to orange, brown, or reddish (from porphyrins — pigments, not blood) and may show a white chalky sediment that settles at the bottom of the litter box. This is not automatically a problem.
Hypercalciuria becomes pathological when:
- Calcium sludge (thick, paste-like precipitate) accumulates in the bladder, causing dysuria, bladder wall thickening, and secondary cystitis
- Uroliths (calcium carbonate stones) form and obstruct the urethra or settle in the renal pelvis
- Urine scalding — the thick calcium-laden urine irritates the perineal skin of rabbits who are not grooming adequately
Excess dietary calcium (particularly from alfalfa hay, which is calcium-rich and not appropriate for adult rabbits), obesity, limited water intake, and sedentary indoor housing all increase risk.
Signs of Calcium Sludge and Uroliths in Rabbits
- Thick, chalky, white or beige urine — the sediment is so concentrated it does not dissolve; you may find white paste on the cage floor or litter box
- Straining to urinate (dysuria) — the rabbit squats repeatedly, produces only a small amount or nothing
- Crying or teeth grinding during urination — calcium grit scratching the bladder wall or urethra causes significant pain
- Blood in urine (hematuria) — mucosal irritation from grit or stones; also occurs with endometrial disease in intact does — differentiate by ultrasound
- Perineal staining and urine scald — thick urine accumulates around the vulva or prepuce, causing wet, inflamed, smelly skin
- Reduced urination frequency or complete cessation (obstruction — emergency)
- Hunched posture and reluctance to move — pain from bladder distension or urinary obstruction
- Weight loss and anorexia — chronic discomfort suppresses appetite
Diagnosis
- Urinalysis with sediment exam — characterizes the quantity and type of crystalluria; also checks for bacteria (secondary cystitis) and blood
- Abdominal radiographs — calcium carbonate stones and heavy sludge are radiopaque (visible on plain radiographs); an easy, inexpensive first-line imaging tool
- Abdominal ultrasound — better characterizes bladder wall thickening, sludge consistency, and stones too small for radiographic detection; also evaluates kidneys for pelvic calculi
- CBC and chemistry panel — checks kidney function (BUN, creatinine), serum calcium levels, and overall health
The AEMV Pet Care Guides, 2024 recommend dietary calcium evaluation and increased water intake as the cornerstone of prevention and management.
Treatment
Dietary management is the primary treatment:
- Switch adult rabbits (over 6 months) entirely to grass hay (timothy, orchard, brome) — NOT alfalfa. Alfalfa is appropriate only for growing kits and pregnant or lactating does
- Remove all commercial rabbit pellets or reduce to minimal quantities; most adult rabbits need pellets only as a supplement, not a dietary staple
- Increase water intake with a heavy ceramic water bowl rather than a bottle; add a second water source; some rabbits prefer running water (pet fountain)
- Offer fresh leafy greens (romaine, kale in small amounts, herbs) that provide water content
Fluid therapy and bladder flushing: In-clinic hydration via subcutaneous or IV fluids, combined with manual expression or flushing of the bladder under sedation, is often needed to clear established sludge.
Pain management: Meloxicam (an NSAID) reduces bladder wall inflammation and makes the rabbit more comfortable during treatment.
Surgery: Large discrete calcium carbonate stones (urolithiasis) that cannot be flushed through the urethra require cystotomy (bladder surgery) for removal.
When to See a Vet
Call your vet today if:
- You see white paste or very thick chalky sediment on the cage floor regularly
- Your rabbit is straining to urinate or crying while urinating
- You see blood in the urine more than once
- Perineal skin appears wet, red, or irritated
Go to the ER immediately if:
- Your rabbit cannot urinate at all — complete obstruction is an emergency
- Your rabbit is pressing its belly to the floor and grinding its teeth
- Collapse, labored breathing, or sudden severe lethargy
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Frequently Asked Questions
Is white sediment in rabbit urine always abnormal? No. A small amount of chalky white sediment in rabbit urine is completely normal — rabbits excrete calcium carbonate crystals through the kidneys routinely. The amount that signals a problem is when the urine looks like thick white paste rather than slightly cloudy liquid, when straining or blood appears alongside it, or when your vet finds bladder wall thickening on ultrasound.
What foods cause calcium sludge in rabbits? Alfalfa hay is the most common dietary culprit — it contains 3–4 times the calcium of timothy or orchard grass hay. Kale (in large amounts), spinach, and some commercial rabbit pellets are also high in calcium. Adult rabbits should eat primarily grass hay. Limiting pellets to a tablespoon or two per kilogram of body weight daily significantly reduces calcium load.
Can calcium sludge in a rabbit's bladder be treated without surgery? Yes, in most cases. Light to moderate sludge responds to increased hydration, dietary changes, and in-clinic bladder flushing under sedation. Surgery is reserved for discrete stones too large to flush and for rabbits that fail to respond to medical management. Your exotic vet's ability to distinguish sludge from stones on imaging determines the treatment pathway.
How much does treating calcium sludge cost in rabbits? An exotic vet visit, urinalysis, and radiographs typically run $150–350. In-clinic hydration and bladder flushing under sedation add $200–500. If surgery (cystotomy) is needed, expect $800–2,000 for the procedure plus recovery. Dietary management — switching to grass hay — costs essentially nothing and prevents recurrence. Ongoing monitoring with annual urinalysis adds $80–150 per year.
How do I prevent hypercalciuria from recurring in my rabbit? The most effective prevention is grass hay as the primary diet (80–90% of food volume), minimal pellets, and maximizing daily water intake. Remove calcium supplements entirely. Keep your rabbit physically active with daily free-roaming time to promote normal voiding frequency. Annual urinalysis lets your exotic vet catch early sludge buildup before it becomes a problem requiring intervention.
Still Not Sure if Your Rabbit Needs a Vet?
When you're not sure if this is wait-and-see or call-tonight, Voyage AI Vet triages in under 2 minutes. Describe what you're seeing in chat, share photos of your rabbit's litter box showing the urine sediment color and consistency, or hop on a live video call if you want a second pair of eyes. Every answer comes with citations to the actual veterinary literature it's pulling from — so you see exactly where the guidance comes from, not just a chatbot's word.