My cat is sick!

Question
For the past week my cat has been acting sick.  Whenever he eats anything, within a few hours he is vomiting it up.  He does not seem as active as usual and just sits around, not even laying down.  He and his brother have not been outside for the past month, so I do not think it is something they have gotten into outside.  The other cat seems just fine.

Answer
Definitely get him to the vet.  I would strongly suggest having blood work done as that is going to be the best indicator of what could be wrong.  He could be having thyroid issues, kidney issues or liver problems, all of which the blood work will be able to tell you.  This is especially likely if your cat is older.  It could also be a foreign body, something he ate that he shouldn't, but since it has been going on for a week I think that is less likely.  Cats can not go for very long without food, they develop hepatic lipidosis, or fatty liver, which can cause problems by itself.  Vomiting can also be caused by pancreatitis.  The list is very long, but fortunately your vet has many diagnostic procedures at their disposal that should make you cat feel better.  

Amanda