Low estradiol on the second day of menstruation is normal within the normal range and should be taken seriously if it is below the normal range. Estradiol is a steroid hormone, mainly secreted by ovarian follicles, corpus luteum and placenta during pregnancy, which plays an important role in maintaining the growth of female genitals, mammary glands and female sexual characteristics. Generally, the normal value of estradiol on the second day of menstruation is about 30-50pg/mL. If estradiol fluctuates slightly and the value decreases, there is generally no need to be overly concerned, but if it is lower than the normal range, it is recommended to go to the hospital for examination in time. Abnormal estradiol values may cause irregular menstruation, infertility, etc., and in serious cases, it may also affect daily life. Therefore, if the symptoms of low estradiol are severe on the second day of menstruation, or if the symptoms persist, the patient should go to the hospital in time for treatment.