If your kid is throwing up, has diarrhea, and isn't drinking any fluids, it's time to see the doctor. Also, go to the doctor if they're having a lot of diarrhea—either 8 to 10 watery poops or 2 to 3 big ones daily—or if the diarrhea doesn't get better after 10 days. If they're vomiting and can't keep any liquids down, that's another reason to consult a doctor.