Does one have to make up for a fast (qaḍāʾ) if one swallowed one's saliva mixed with a tiny bit of blood from the gums, after spitting it out and purifying one's mouth from it, and then felt the taste of blood in one's saliva again?

Swallowing blood intentionally is forbidden and invalidates the fast. However, if blood reaches the throat unintentionally, it does not break the fast. It is obligatory to spit out the blood, not swallow it. If one presumes that the saliva is free of blood and swallows it based on that presumption, the fast is valid. Some scholars hold the view that a person who is constantly overwhelmed by blood in the mouth is excused, so they are not obligated to spit it out or wash their mouth, and swallowing it does not break their fast.