It is not permissible for a person
to swallow blood intentionally because it is Haram (prohibited). Allah (Exalted be He) says:
Forbidden to you (for food) are: Al-Maitah (the dead animals - cattle - beast not slaughtered), blood
However, if blood is swallowed unintentionally, there is no harm.May Allah grant us success. May peace and blessings be upon our Prophet Muhammad, his family, and Companions.