How many days should a new cat be isolated from its old cat before it is safe to do so?
1. New and old cats are usually separated for about seven days. During this time, the two cats should be placed in separate rooms. The new cat will gradually become familiar with the new home environment and get used to the smell of the old cat. The old cat will also get used to the arrival of the new cat. Generally, the two cats may accept each other after 7 days.
2. When you first meet a new cat, the old cat may not be very friendly to it, as it may feel that its territory has been threatened. At this time, the owner should soothe the cat's emotions, play with it more, and pet it.
3. If the two cats still cannot accept each other after about 7 days, it is recommended to extend the isolation period to about 20 days. The owner should spend more time with the two cats to make them feel safe. Generally, the cats will accept their companions quickly. 
Why should a new cat be separated from an older cat?
Because cats have a strong sense of territory and are solitary animals, especially male cats, a new cat may be attacked if it is not isolated, which could lead to stress reactions such as vomiting, diarrhea, and loss of appetite. Therefore, isolation is necessary to allow them to adapt to each other.
