Dog has diarrhea, won't eat. Can I give antibiotics without food?

I'm sorry to hear that Nicco hasn't been feeling well, but I'm glad to hear that you've already sought veterinary care. It is most commonly recommended to give antibiotics with food since this will lessen the chance of developing an upset stomach with vomiting and diarrhea as a side effect of the antibiotics. In this case, however, Nicco is already having diarrhea and experiencing a loss of appetite. It should be just fine to give him the antibiotics (metronidazole or Flagyl, I assume, given the bloody diarrhea) without food until he is eating normally again. You can also ask your vet about offering Nicco a bland diet of boiled white meat chicken and white rice since he is refusing to eat the Royal Canin gastrointestinal low fat diet. If your veterinarian approves this plan, a typical rule of thumb is to feed 1 cup of a 50:50 chicken/rice mixture for every 10 pounds of body weight per day, divided into 3-4 smaller meals.

If Nicco is still refusing to eat, experiencing bloody diarrhea, or begins to vomit by tomorrow, I recommend calling your vet since he may need to be reevaluated with additional diagnostic testing or supportive treatments.

I hope this helps and that Nicco feels better soon!