Assalaamu alaikum,
What is the Islamic ruling regarding bone marrow donation?
Jazak Allah khair

All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger.

We came to know that the reality of bone marrow donation is a kind of donating some blood cells, and if the matter is so, then –Allaah Knows best –it takes the ruling of blood donation.

Blood donation is indeed permissible in case of necessity; for more benefit, please refer to Fatwa 82197.  

Allaah Knows best.