he is most likely having some infection. BP tends to get fluctuated during these periods. he might need some fluids. but your question is little incomplete regarding your father. please feel free to share more about his fever and symtoms, than i could come up with a diagnosis. do he have fever with chills ?
since when is the fever ?
any urine burning, chest pain ?
acidity or constipation?
need a detailed chat
Next Steps
private consult with me for detailed treatment protocol with medicines