Cat vomits for two days...

My cat started throwing up two nights ago. She has not stopped. I took her to the vet today, he gave her subcutaneous fluids and also some pills to try and get whatever is causing her to throw up through her system. In the beginning a hairball popped out but since then it has been recently eaten food or just a liquidy like substance. I am very worried. Could she have eaten something that is blocking her. What else could it be? He wanted to do blood tests but I opted to wait and see what is happening in 24 hours. Should I have an x-ray done first, if she isn't better?:confused:

I suppose the vet would have mentioned if he thinks she ate something poisonous.

That's the only thing that came into my mind.

Vomiting can be very many reasons- most of them harmless, but I also would take her back to the vet.