Cat throwing up daily

by Jennifer
(Washington,NC,Beaufort County)

I have a 13 year old male cat tigger. He has been throwing up at least once a day since February. Well, let go to the beginning. Around 2 years ago I found out Tigger was diabetic. So he went on insulin. In January 2008 the Dr. said his sugar levels were ok, to take him off the insulin for a week and re-check him. Well we did and his levels were ok, so he is no longer on insulin. I think changing his diet helped. However, in February he started throwing up liquid of different colors. I have even seen a speck of blood in it. The Dr. has tried powder in his food, tested sugar ,thyroid, kidney and x-rays with barium. Only a few times has he thrown up undigested food. All of his tests look fine. Do you have any suggestions for me?
Thank you
Jennifer