Cats typically grow their fur back in about a month after a shave, and it usually takes two to three months for it to fully grow back. However, long-haired cats may take up to six months to fully grow their fur back after a shave. To help your cat's fur grow back faster, you can feed them nutritious food, such as coat-enhancing cat food or canned food. These foods are rich in protein and vitamins, which can provide essential nutrients for your cat's body and coat. 
After a cat is shaved, it becomes more sensitive to temperature changes, especially when the temperature drops. Without the protection of its fur, it is easily chilled and needs its owner to keep it warm. Regular sun exposure and brushing its fur also promote blood circulation and healthy new fur growth.
