Physiological period refers to the menstrual period, during which metabolism is slow. Under physiological circumstances, if fertilization and implantation do not occur after ovulation, the corpus luteum undergoes atrophy and degeneration, resulting in a significant decrease in blood levels of estrogen and progesterone, leading to spasmodic contraction of the small spiral endometrial arteries, ischemia, degeneration, necrosis, and ultimately exfoliation of the functional layer of the endometrium, rupture of the blood vessels and bleeding, that is to say, enter into the period of menstruation, which is the so-called physiological period, and the normal duration of about 3 to 5 days. Progesterone has the effect of enhancing metabolism, and estrogen and progesterone levels drop significantly during menstruation. The drop in progesterone levels will cause basal metabolism levels to decrease compared to other periods in the menstrual cycle. However, the basal metabolic rate during menstruation may be regulated by a combination of other factors, and the speed of the metabolic rate should be determined on a case-by-case basis. If metabolic rate is abnormal, it is advisable to consult a doctor to identify the cause and have it treated by a doctor.