Does Your Fast Break If You Bleed?
Question

I want to ask about the amount of blood coming from the body of a person which invalidates the fast. I suffer from piles (hemorrhoids). That has been for a long time and is not regular, and it may be accompanied by bleeding, the amount of which is approximately half a coffee cup.
Praise be to Allah.We ask Allah to bless you with a speedy recovery. 
Does bleeding break your fast?
Because this bleeding is caused by sickness, your fast is still valid, and you do not have to do anything even if the blood is a large amount, so long as it comes out without you doing anything (to cause it). 
Conditions of the blood that invalidates the fast
The guidelines concerning the blood that invalidates the fast are as follows: 

If the blood comes out as the result of a person’s actions or choice; this is subject to further discussion: 

(A) If the blood comes out by means of cupping, this invalidates the fast, because the Prophet (peace and blessings of Allah be upon him) said: “The cupper and the one to whom cupping is done both break their fast.”
(B) If it comes out by a means other than cupping, such as venesection (opening a vein). If the amount is large and that has an effect on the person’s body, then this invalidates his fast (such as donating blood). If the amount is small and it does not harm the person, then it does not invalidate his fast, such as the small amount of blood that is taken for testing.

If the blood comes out through no deliberate action, such as an accident or nosebleed or an injury to any part of the body, his fast is still valid even if the amount of blood is large. (Fatawa Islamiyyah, 2/132)

But if the blood that comes out through no deliberate action is of such a large amount that he becomes weak and unable to fast, then it is permissible for him to break his fast and he should fast another day to make up for it.
For more, please see this answer: 94402 .
And Allah knows best.