http://www.vetstreet.com/care/anemia-in-cats
I posted a link for you to check out. My concern with your anemic kitten, is why is he anemic in the first place. My mind runs to having a severe infestation of parasites, so my next question is did they give him a dewormer and take care of the problem, and also check for coccidia. Does he have diarrhea? The best thing you can do is keep feeding him by getting food into him any way you can. Any wet food, diluted with goat’s milk or kitten formula for the extra nutrition and also more fluid. I always add water to my cats’ wet food — it can’t hurt and they love the ‘soup’ it makes. I hope this helps your poor little guy. Keep us posted on him please.
I wanted to add also, you can add pedialyte to his food to up his electrolytes, raw egg, even some baby vitamins. Did you check him for fleas? Fleas can cause anemia and kill an animal fast, so if you have to bathe him with Ivory soap or Dawn, it will kill the fleas. Get a flea comb and comb eggs out also. Make sure you dry him with a blow dryer, so he does not get a chill.