The female cycle is the time between the first day of the 2 menstrual periods, which is about 28 days for most women, some may be early and some may be late. But as long as each time is fixed, it is normal. Each woman has her own menstrual cycle, which may be related to heredity. If your menstrual cycle is usually early or late, it is not normal and you need to go to the hospital for a sex hormone test. If your menstrual cycle is prolonged and your menstrual flow is low, you should consider if you have polycystic ovary syndrome, it is best to go to the hospital for ultrasound and blood tests to confirm the diagnosis.