Accordingly, a woman experiencing istihādah may find herself in one of three situations:

The first situation: She had a well-known menstrual habit before the onset of istihādah—for example, she used to bleed for five or eight days at the beginning or middle of each month, and she knows both the length and timing of that habit. In this case she should remain in seclusion for the duration of her former habit, abstaining from prayer and fasting, and the rulings of menstruation apply to her. Once those habitual days are over she performs a full ritual bath, resumes the prayer, and treats any remaining blood as istihādah. This is based on the Prophet’s ﷺ instruction to Umm Ḥabībah: “Stay away from prayer for the same number of days that your menstruation used to detain you, then bathe and pray” (Muslim); and on his ﷺ words to Fāṭimah bint Abī Ḥubaysh: “It is only a vein; it is not menstruation. When your period arrives, refrain from prayer” (agreed upon).

The second situation: She has no fixed habit, yet her blood is distinguishable—part of it bears the characteristics of menstrual blood, being dark, thick, or having a distinct odor, while the rest lacks those traits, appearing red, thin, and odorless.