Why Is My Cat Not Using the Litter Box? Causes, Warning Signs, and How to Help

Quick Answer: There are two main reasons a cat may stop using the litter box: medical problems (such as feline idiopathic cystitis, urinary blockage, constipation, and arthritis pain) and environmental or behavioral issues (such as a dirty litter box, not having enough litter boxes, or competition for litter box access in a multi-cat household). If your cat stops using the litter box, rule out a medical problem first. Once medical causes have been ruled out, many environmental and behavioral issues can be addressed by cleaning the litter box more often or adding more litter boxes.