While your vomiting and nausea may pass quickly, there are some situations in which you should contact your doctor. Even a mild case of the flu may become serious if the sick person becomes dehydrated. Call your doctor if you or your child experience the following:  You are unable to keep down any food or liquid You have vomited more than three times in one day You received head injury before the vomiting began You have not urinated in six to eight hours For a child under six: vomiting lasts more than a few hours, they have diarrhea, signs of dehydration, a fever, or they haven't urinated for four to six hours For a child over six: vomiting lasts longer than 24 hours, diarrhea combined with vomiting lasts longer than 24 hours, there are any signs of dehydration, fever higher than 101°F (38.3°C), or they haven't urinated for six hours In some cases you or your child will need immediate medical attention. Call 911 or your emergency services right away if you or your child experience the following:  Blood in the vomit (appears bright red or looks like coffee grounds) Severe headache or stiff neck Lethargy, confusion, or decreased alertness Severe abdominal pain Rapid breathing or pulse

Summary:
Know when to contact your doctor. Know when to call emergency services.