Environmental -
~ A change in the kind of litter you use
~ Adding new animals or family members to the household
~ An uncomfortable location of the box that doesn't allow for privacy and multiple escape routes
~ Negative associations - your cat may have been upset while using the box or may associate the box with painful elimination, even if their health is normal
Medical -
~ Urinary Tract Infection (UTI) - If your cat frequently enters the litter box but only produces small amounts of urine, they may have a UTI. The urine may also have a "pink" color to it.
~ Bladder Stones or Blockage - Your cat may frequently enter the litter box, but also experience pain and meow or cry when trying to eliminate and their abdomen may be tender to the touch. This is very common in male cats who eat mainly dry food.