Wa `alaykum As-Salamu waRahmatullahi 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:
Answering your question, we would like to cite the following fatwas published on www.islamqa.info:
It is not permissible for the Muslim to swallow blood, whether it is a little or a lot, in Ramadan or at other times, because blood is haram, unless it is swallowed by mistake or involuntarily, in which case there is nothing wrong with it. Allah says in the Qur’an:
“He has forbidden you only the maytah (dead animals), and blood, and the flesh of swine, and that which is slaughtered as a sacrifice for others than Allah (or has been slaughtered for idols, on which Allah’s Name has not been mentioned while slaughtering). But if one is forced by necessity without willful disobedience nor transgressing due limits, then there is no sin on him. Truly, Allah is Oft-Forgiving, Most Merciful” (Al-Baqarah 2:173)
The scholars of the Standing Committee for Issuing Fatwas were asked:
Sometimes an individual may get a cut and he licks the blood that is coming out, which results in his swallowing the blood, or his gums bleed, so he swallows the blood that comes out. Is there anything wrong with that?
They replied: It is not permissible to swallow blood deliberately because it is haram. Allah says:
“Forbidden to you (for food) are: Al‑maytah (the dead animals — cattle — beast not slaughtered), blood…” (Al-Ma’idah 5:3)
With regard to swallowing it unintentionally, there is no blame in that case. (Fatawa al-Lajnah al-Da’imah, 22/272)
Allah Almighty knows best.