Calcium and Urinary Stones in Rabbits: Getting the Diet Right
Unlike most mammals, rabbits absorb dietary calcium in near-direct proportion to what they eat, then excrete the surplus through urine rather than finely regulating intestinal absorption. This quirk, well documented in a study by Clauss and colleagues on calcium metabolism and urinary sludge in rabbits (research on Google Scholar), explains why a diet too rich in calcium favours the formation of sludge and urinary stones. Our general guidelines are in the rabbit food section.
Why some rabbits are more at risk
A rabbit that is sedentary, overweight or drinking too little concentrates its urine more, which favours the clumping of calcium crystals. Pellets heavy in alfalfa, legumes, and an excess of high-calcium vegetables such as radish tops or kale, fed in large amounts, push calcium intake beyond what is needed.
Adjusting the diet to lower the risk
The base should stay a grass hay (Crau, meadow, second-cut) rather than alfalfa for non-breeding adult rabbits, since alfalfa is markedly higher in calcium; see our guide to choosing the right hay. Limit alfalfa-based pellets, rotate greens instead of repeating the same higher-calcium ones, and ensure permanent access to clean water to support good urinary dilution.
When to see a vet
Thick, chalky urine or difficulty urinating warrants a prompt vet visit, with an X-ray if needed to confirm a stone. An overweight rabbit stacks up risk factors: low activity plus a too-rich diet; our guide to an overweight rabbit diet plan helps correct the ration alongside these steps.
Frequently asked questions
Should all calcium be removed from the diet?
No, calcium remains essential for bones and teeth; the goal is to avoid repeated excess, not to eliminate it.
Is alfalfa forbidden?
Not entirely: it suits growing young rabbits well, but should stay limited for a sedentary adult.
Is a rabbit that drinks little more at risk?
Yes, concentrated urine makes crystal formation easier; a large-capacity water dispenser plus a bowl as backup encourages good hydration.
This guide is part of Planète Pets’s Rabbits universe. Our advice is general in nature: for any health concern, your veterinarian remains the only reference.