Answered by Sidi Fadi Qutub Zada
Does drawing blood, as for a blood test, invalidate ablution?
In the name of Allah Most Compassionate and Merciful
Blood that is withdrawn vitiates the ablution, just as blood that flows from a wound does. Imam Ala ad-deen Abidin says in his fiqh work al-Hadiyya al-Alaiyya, page 26: “and filth that flows from a wound (f: invalidates the ablution), even if it does not flow out, but is removed (or withdrawn).”
And Allah alone gives success