Menstruation had many tremendous psychological response in adolescent. And there are many myths prevalent regarding menstruation. So this study was conducted with the aim to study menstrual pattern in adolescent school going girls and association of menstrual blood flow with their BMI, diet, sports activities and gadgets. This study is a descriptive type of cross-sectional study in which adolescent girls who attained menarche were included. Present study was carried out on in government schools Jaipur City (Rajasthan) on 1233 girls aged between 13 to 19 years. BMI was significantly associated with amount of blood loss. Girls whose BMI was <18.5 kg/m2 or underweight had moderate to severe degree of dysmenorrhoea compare to those BMI 18.5-24.9 kg/m2. Proportion of girls involved in sports activities were having less amount of blood loss compared to those who were leading sedentary life. B So it can be concluded that BMI has direct co-relation with menstrual blood loss; the girls involved in sports had less amount of menstrual blood loss.