In India, hyperthyroidism accounts for 5 per 10,000. The seriousness of thyroid disorders should not be underestimated as thyroid storm, thyrotoxicosis and myxedema coma can lead to death in a significant number of cases. In this study, 50 female patients of above 18-year-old were included in the study (Pre- and Post-menopausal), whereas patients who have undergone radioactive ablation and thyroidectomy were excluded. Blood samples were collected and thyroid tests like TSH, T3, T4 were performed by the method of chemiluminescence enzyme immunoassay. Complete Blood Count (CBC) is performed to check the values of Hb, RBC, WBC, Neutrophil, Basophil, Eosinophil, Platelet, Lymphocyte. Liver function tests like SGOT and SGPT were performed to find whether carbimazole induces any liver damage. Thyroid tests and CBC values were noted down at the time of diagnosis and during the course of treatment. Out of 50 hyperthyroidism patients, 2 patients (%) experienced Neutropenia and Agranulocytosis. According to a study done by Davies [6] Carbimazole shows rare adverse effects like neutropenia and agranulocytosis. In our study, 2 patients (6.8%) experienced neutropenia and agranulocytosis. They have symptoms like blisters in mouth and fever. When their CBC were done, it was found that their neutrophil count and WBC has reduced. When neutrophil count is reduced, body’s ability to fight off foreign body reduces and it ensures easy attack by micro-organism.