Are secretions with red threads considered menstruation if the menstrual cycle is disturbed and irregular? And are the first days in which the blood is scant, brownish, and yellowish considered menstruation? And if the period exceeds fifteen days, is what comes after that considered استِحاضَة (istihāḍah - irregular vaginal bleeding outside of menstruation)?

The minimum duration of menstruation according to the majority of scholars is one day and one night. If the bleeding period reaches a total of one day and one night, then it is considered menstruation. If it does not reach that duration, it is not considered menstruation according to the majority. However, according to the Malikis, it is considered menstruation even if it occurs for a single instance. When a woman sees blood, she should stop praying and fasting. Purity that occurs intermittently during the menstrual period is considered valid purity. If the brownish discharge (kudra) is continuous with the blood, it is considered menstruation. If the days of bleeding and the intermittent purity do not exceed fifteen days, then all of it is considered menstruation. However, if its duration exceeds fifteen days, then the woman is considered to be suffering from irregular bleeding (istihadha). In this case, she should refer to her previous habitual period, or apply the criterion of distinguishing between menstrual and non-menstrual blood, or observe the predominant habit of women.