 [ Symptoms ] my son was on day 8 of 1 000mgday amoxicillian and he spiked a fever should i be worried  he presented with high fever and sore throat and was treated for strep his fever broke the second day but on day 8 of antibiotics he spiked a fever the ibuprofen i gave him wore off and the fever has not returned should i return to the doctor [ Disease ] fever is the body is response to inflammation or infection amoxicillin is only effective for a bacterial infection like strep it is absolutely no effect on viruses a person can contract a virus anytime even while taking an antibiotic fever does not really shock or bother medical professionals as much as it does parents but i cannot blindly tell you the significance of this brief transient fever i do not know anything about your son what you really mean by a spike so when in doubt call his medical provider    someone who knows him his particular case and someone that can offer you the patient specific advice that you really need