The thyroid is an endocrinal, butterfly-shaped, and biggest gland in the neck which makes and stores hormones that help in the regulation of blood pressure, heart rate, and body temperature and also help in the regulation of growth and rate of chemical reactions (metabolism) in the body. Hypothyroidism is associated with decreased thermogenesis, decreased metabolic rate, and has also been shown to correlate with a higher body mass index (BMI) and a higher prevalence of obesity. The present study was undertaken to evaluate the BMI at the time of diagnosis in hypothyroid patients and compare with that of normal individuals. A Case control study was conducted at Dinajpur Medical College Hospital, Dinajpur Bangladesh from January 2020 to December 2021. Out of 150 hypothyroid subjects 133 were females and 17 were males. Out of 150 normal individuals 70 were females and 30 were males. All subjects were in the age group of 20-40 years. Height is measured with Harpenden stadiometer, & weight is measured with standard weighing machine. BMI was calculated, data of T3, T4 & TSH levels were collected & compared between normal and hypothyroid subjects. It was found that hypothyroid subjects had a higher body mass index than the normal individuals. Hence maintenance of thyroid hormones at normal level and regular monitoring of BMI in Hypothyroid patients will help in early detection and prevention of obesity and its related complications in future. Hence maintenance of thyroid hormones at normal level and regular monitoring of BMI in Hypothyroid patients will help in early detection and prevention of obesity and its related complications in future. Awareness of weight reduction and regular physical exercise are to be advised to patients with hypothyroidism.