Fever is perhaps the most ancient hallmark of disease since the beginning of civilization itself, fever has been regarded as a prime clinical feature of illness. Fever is the body’s response to variety of factors that is reflected in on increase body temperature above normal range. Platelets are fragment of the large megakaryocytes, produced in the bone morrow under influence of thrombopoetin, a chemical made by the liver and kidney. Each megakaryocyte makes about 4000 platelets. The platelets then enter circulation and have a life span of 7-10 days. They are cleaned from body by spleen and to lesser extent, the liver and bone morrow. A normal human platelet count ranges from 150,000 to 450,000 platelets per microlitre of blood. Thrombocytopenia defined as platelet count less than 150,000 per micro liter. Which is further divided in mild (100,000- 150,000 per micro liter), moderate (50,000-100,000 per micro liter), sever (< 50,000 per micro liter). Hence based on above findings the present study was planned for Assessment of Prevalence of Thrombocytopenia in Patients Suffered from Fever from Bihar Region. Total 50 cases of the patients suffered from fever with thrombocytopenia were enrolled in the present study. The present study was planned in Department of General Medicine, Nalanda Medical College and Hospital Patna, Bihar, India. Detailed examination of various systems was done. Routine investigation was done, the specific and special investigations were done as and when indicated. The data generated from the present study concludes that thrombocytopenia is a challenging problem in clinical practice and is usually caused by infectious diseases. In this study, malaria is the most common cause of febrile thrombocytopenia closely followed by dengue fever, especially in epidemic scenarios. Other infections such as enteric fever, scrub typhus, chickungunya fever, viral hepatitis, leptospirosis and sepsis also contribute to cases of febrile thrombocytopenia but in lesser numbers.