Wa `alaykum as-Salamu wa Rahmatullahi wa Barakatuh.
In the Name of Allah, Most Gracious, Most Merciful.
All praise and thanks are due to Allah, and peace and blessings be upon His Messenger.
In this fatwa:
You should know that only menses invalidates fasting. As for what you have described in your question, it is chronic bleeding which only requires renewing ablution (wudu) for each Prayer and fasting is not affected at all.
In his response to your question, Sheikh Ahmad Kutty, a senior lecturer and an Islamic scholar at the Islamic Institute of Toronto, Ontario, Canada, states:
She should follow her pattern of menses as well as her sound judgment. If it is not menses, it is a case of chronic bleeding known as istihadah, which can be translated as semi-menses. In the case of istihadah, she should fast and pray. However, she is required to wash her private parts and renew her wudu for each Prayer.
Allah Almighty knows best.
Editor’s note: This fatwa is from Ask the Scholar’s archive and was originally published at an earlier date.