How old do newborn kittens have to be to leave their mother?

Newborn kittens need to stay with their mother until they are six weeks old. The mother's milk is the healthiest option for the kittens, and someone may have to feed them with a bottle if the mother is not there or refuses to feed them.

A mother cat may refuse to feed her kittens if they are away from her too long or if there has been too much interference by unknown humans. She may also refuse to come back to her nest if she sees humans nearby, and a distance of at least 35 feet between humans and a nest with newborn kittens is recommended.