My 1 year old has had diarrhea for 3 weeks. they took stool sample and blood work and found nothing. she had a fever for the past 3 days. any suggesti?

Hospitalize: It sounds like she is getting worse, and needs to be evaluated for dehydration.

Chronic Diarrhea: Diarrhea can be a result of infection, malabsorption, food allergies/ intolerance, transient lactose intolerance etc., etc. Usually viral GI infections do not last more than a week. Also keep in mind infection of other systems--- lungs (pneumonia), urine (UTI) etc should be ruled out too!