Can your child get high fever while on antibiotics?

It is possible for a child to get a fever after being on an antibiotic for three days. There are several reasons. A few of those reasons are that the child could be sick with a virus and not a bacteria, in which case the antibiotic would be useless. Another scenario is that the bacteria is resistant to the particular antibiotic and that a different one is needed. In either case, you should follow up with the child's physician.