Low estrogen refers to the absence of menstruation within 14 days after progesterone injection. In this case, low estrogen level should be considered, which should be combined with the sex hormone six test to further clarify what causes low estrogen level. If follicle stimulating hormone and luteinizing hormone are elevated in the sex hormone test report, it is considered that ovarian function is declining and a health check is needed to consider hormone replacement therapy if necessary. If folliculopoietin and luteinizing hormone are both low, central amenorrhea should be considered, and gynecological examination should be done. If a woman’s estrogen level is low, it may easily cause hot flashes, sweating, insomnia, irritability, bone and joint pain, and even risk of osteoporosis and fracture, or recurrent urinary tract infections, recurrent vaginal inflammation, etc.