Although fever is most commonly caused by bacterial infection there are multiple other conditions that can cause fever. It can be caused by viral infection. It can also be caused by other non infectious disease. Patients with malignancy, inflammation (such as gout or arthritis), or clots in veins can present with fever. Occasionally medications themselves can cause fever. If fever is not caused by infection antibiotics will not help. Instead they may cause side effects such as diarrhea and allergic reactions. We want to determine whether simple blood test (procalcitonin) can help us to make a difference between fever caused by infection and fever caused by others (above mentioned) non-infectious problems. We also want to determine whether such test would help us to reduce unnecessary antibiotic use and help us to find faster the real cause of the fever.