Is swallowing some blood intentionally after trying to expel it for hours considered a fast-breaker, and is it obligatory to make up the fast on the second day of Shawwal or on any day before the coming Ramadan?

One must be careful not to swallow blood while fasting, as it invalidates the fast and is forbidden even outside of fasting days. If the swallowing was intentional, the fast is invalidated and must be made up before the next Ramadan, and it is recommended to do so promptly. However, if it was unintentional, the fast is not invalidated, because the blood seeped in without the fater's choice.