The frequency that a cat should be dewormed depends on its potential exposure to parasites, which are usually acquired by exposure to infected rodents, fleas or the feces of infected cats. Some veterinarians recommend a preventative dewormer every six months.
Indoor cats that live in clean homes free of rodents and fleas have a low risk of contracting parasites, so they may need to be dewormed less frequently than cats that are allowed outside. Kittens generally need preventative deworming at six weeks. Fecal tests can be used to help diagnose parasite infections and determine how often a cat needs to be dewormed. Veterinarians are typically familiar with the local risks and can help owners develop the best deworming schedule for their cats.