He got his rabies shot two days ago just wondering if this has caused him to loose his appetite or if I need to take him in to get checked, because he also has diarrhea

I'm always leery of making causal connections that might not actually exist. My dogs had rabies shots every year their entire lives and never lost their appetites or got diarrhea. Same with my cats and horses. This sounds like a quick trip to the vet would be a good idea just to rule out infections and other problems.

I agree, reactions to rabies shots are pretty rare, all though not entirely uncommon. I agree, a trip to the vet is in order. Was he also vaccinated for Parvo?