Hello! Thanks for being with us. There are thousandths of causes of fever but we can not test for all. Tests should be individualized according to the symptoms at present,age,sex,residence,occupation,past medical illness,family history and findings on clinical examination. As you have not provided with any of these,it is little difficult to come to the differential diagnosis. Here i will provide you some plan,hope it will help you. Now,you stop all the drugs for few days.Measure fever whenever it comes.Keep record of fever charting.Sometimes drugs also cause fever hence if it is due to drugs it will go out. If fever still persists,get a revisit with the physician. I would like to mention some rare causes of fever for which you may need to work out. 1.Occult tuberculosis. 2.Chronic drug resistant malaria. 3.Malignancies. 4.Brucellosis 5.Parasitic infections 6.Urinary tract infections 7.Autoimmune conditions like SLE,vasculitis syndromes 8.Hyper/hypothyroidism 9.Infective endocarditis. 10.Rickettsia So additional investigations which you should do is HRCT chest and abdomen,Stool and urine routine micro,blood cultures,ESR,CRP,TB-PCR or TB-GOLD,Weil felix test,Brucella antigen test,thyroid profile,2decho,ANA,dsDNA. In this case physician has to give more time for evaluation and he is the who can help more. Hope you have satisfied with the answer. Feedback and more queries are most welcome. Wish you good health.