Ferrets fed generic cat foods containing mainly plant protein are particularly susceptible to bladder stones. Digestion of protein produces chemical compounds that must be excreted in the urine. The products formed from the digestion of plant proteins make the urine alkaline. Magnesium salts form struvite crystals in alkaline urine, and stones form when crystals accumulate and stick together. These cause complete obstruction and death in untreated male ferrets, and chronic problems with partial obstruction in females. Treatment generally consists of surgical removal of the stones.

Eating meat protein makes the urine more acidic, and reduces the likelihood of bladder stones forming. Urinary tract infections increase susceptibility to stones. Ferrets with bladder infections should be treated with appropriate antibiotics and fed diets that contain the best quality meat protein possible.