SHAFAQNA – The Grand Ayatollah Sistani answered a question about the duty of a person whose gum bleeds continuously.
Question: What is the duty of a fasting person with continuous bleeding gum?
The Grand Ayatollah Sistani: If in sleep or similar to that the blood enters the throat and caot prevent it, there is no harm to fasting; but if due to difficulty, swallows the saliva with unabsorbed blood and does not throw it out (of the mouth) then the fasting is void (Baatel).
Source: PERSIAN SHAFAQNA