I change my cat's litter box once a week. I make sure to scoop out the litter and dispose of it in the trash regularly, and I also replace the litter with fresh litter every week.
If you use a clumping litter, it's best to scoop the box daily and change it out completely at least monthly. If you have more than one cat, it may be best to change the cat litter more often, every 2-3 weeks.
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