when should we take antibiotics means after how many days of fever or when it's necessary

A. So antibiotics are specifically taken as per doctors advice and it is only given in the case when there is an infection detected otherwise antibiotics should not be taken or given because it ultimately load on the liver is given for no use from your side if it’s a normal fever it can take three days to subside and if not then it could be a viral or something then you should consult your doctor