Question: how long do kittens have runny poop?
Answer: Sometimes, it comes and goes quickly. Other times, it can last for days, weeks, or months, or come back on a regular basis. Diarrhea that lasts for 24 to 48 hours probably won't cause a problem unless you have an older cat or a kitten. But if it lasts longer, your cat can get dehydrated, which can be dangerous.