Purity: Fasting and Istiḥāḍah

Practical Laws of Islam as per the teachings of Ayatullah Sistani

Ruling 415:

The recommended precaution is that during the entire day that a mustaḥāḍah is fasting, she should prevent the blood from coming out as much as she can.

-Ayatullah Sistani, Practical Laws of Islam, Purification (Taharah)