It is best to feed catnip once a week, just a little each time. Do not feed it too frequently or too much, otherwise it will easily cause the cat to have difficulty breathing, be immune to catnip, or have other side effects. Moreover, cats in estrus and pregnancy cannot be fed catnip, as it will cause miscarriage, premature birth or aggressive behavior. It is best not to feed catnip to kittens under six months old.