Menstruation is possible when the thickness of the endometrium reaches 8mm or more, but it is not absolute and depends on the specific situation.
The endometrium will undergo a cycle of proliferation, secretion and shedding under the influence of hormone level changes in the body, and after the endometrium reaches a thickness of 8mm or more, menstruation will be possible. During a menstrual cycle, the endometrium goes through 3 phases: proliferative phase, secretory phase and menstrual phase. The thickening of the endometrium under the action of estrogen and progesterone is a prerequisite for menstruation.
When the endometrium thickens to 8mm or more, menstruation is possible, but it is not absolute, e.g. perimenopausal women may not reach 8mm and may have normal menstruation.
If a woman has abnormal menstruation, it is recommended that she go to a regular hospital for endometrial thickness examination and menstrual cycle evaluation, avoiding blind treatment on her own, which may lead to adverse consequences.