The first menstrual period usually lasts for 3 to 7 days.
Girls experience their first menstrual period at the age of 12 to 14, which is one of the signs that a woman has entered puberty. When menstruation occurs for the first time, the ovaries are not fully developed and the reflexes of the pituitary and gonadal axes are not yet perfect, which may result in abnormalities in the menstrual cycle and irregularities in the cycle and its duration, but menstruation will gradually become more regular as the ovaries become more mature.
The duration of the first menstrual period varies from person to person and cannot be generalized. Some people may have their period end after only 1 or 2 days, while others may have it off and on for a long time, so you can observe it for a while and consult a doctor if you feel unwell.