first off you want to check for signs of dehydration including fewer wet diapers less play sunken eyes sunken fontanelle (soft spot on baby's head) loss of skin turgor and dry mucous membranes. the fact that your baby isn't eating enough for adequate growth is another consideration. six months is also the time to start solids which is important for development and nutrition. this webmd article discusses various causes of diarrhea in babies. i would contact your doctor to find out if he or she wants you to come back in or get referred to a gastroenterologist. i think your gut is saying something isn't right -- and that is very important in my book.
my 6mth old weighs only 12. 8 lbs and has had diarrhea for 3 weeks what tests could be done to help determine the cause. after the first week i took her to the doctor and they diagnosed her with ear infections. she started augmentin a week later i took her back because she was still having diarrhea and loss of apetite and fevers ranging from 99. 0 - 102. 7 rectally. her wbc was 9. 5 and they said it was probably a virus. now another week has passed and she isn't better. no fevers that i have noticed but she is having watery bowel movements about 6 times a day and is only eating about 16 oz of formula a day.