The thyroid gland is the largest endocrine gland of human body. It synthesizes and secretes two major hormones–3, 5, 3 triiodothyronine (T3) and thyroxin (T4). Thyroid hormones are essential for the normal development, differentiation, metabolic balance and physiological function of virtually all tissues. Thyroid hormones also play an important role in hemoglobin production in adult, maturation of hemoglobin in fetus and in erythropoiesis. They cause hyper proliferation of immature erythroid progenitors and induce erythropoietin gene expression thus increasing secretion of erythropoietin leading to increased erythropoiesis. Thyroid disorders are accompanied by red blood cell abnormalities. Thyroid disorders can induce different effects on various blood cell lineages. The study was conducted on 200 patients with established thyroid dysfunction admitted in the medical wards or coming to outpatient department at Sir Takhtasinhji General Hospital, Bhavnagar.