my grandson who is 5 has just started school but has been off all week with temperatures, thirsty, no interest in food, he suffered a serious bout of tonsilitis in December, he is not a good eater, his parents have had blood tests done, is there anything we are not looking at? could his iron level be low?
Fever itself causes prostration and weakness to cause weak appetite.  Sick kids eat less. Iron deficiency is associated with poor appetite no doubt, but also causes easy navigability, pica etc. and usually not associated with fever as it is not an infection but deficiency. So look for infection treatment. Keep him HY Chat Doctor.  If he is playing, it may just be a self limiting viral infection.