My cat is tired and not eating after vet allergy shot, why?
Hello. I am sorry Simba is not feeling well. It is possible that Simba was incubating, or had a low-grade infection. The allergy shot was actually a steroid injection that lowers the ability of the immune system to respond to an infection, essentially making the infection worse. So, this is not a behavior change, Simba just is under the weather. Hopefully, the antibiotics will keep things from getting worse, but if Simba does not pick up in a couple of days, please call your veterinarian. He may need a change in antibiotics, or be placed on an antiviral medication. As long as he is eating a little each day, he will be OK, but if he refuses all food, have him seen as soon as possible. I hope Simba is feeling better soon. Thanks for using Petco Pet Education Center, formerly Petcoach.
Updated on September 23rd, 2025