ANSWER:

What you do unknowingly you are not accountable for, however, if you deliberately swallow blood, the fast is invalid and you must make it up. 

Mucus with saliva doesn’t impact fasting.

Please advise if Saliva mixed with blood or mucus during Salah or Fasting is shallowed will invalidate or not?

Fasting | September 27, 2020 1:46 am
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The Messenger of Allah (blessings and peace of Allah be upon him) said to us: “O young men, whoever among you can afford it, let him get married, for it is more effective in lowering the gaze and guarding one’s chastity. And whoever cannot afford it should fast, for it will be a shield for him.” Sheikh according to this hadees can single man fast whole days or 15 days
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If i made intention before sleep to fast (missed fasts of Ramadan) next day and I don’t wake up at suhoor time I wake up late so now do i have to fast without suhoor or is it not allowed to fast without suhoor in any case?