When one of Jehovah's Witnessses accepts blood or blood fractions, where do they come from?
Jehovah's Witnesses do not donate blood.
Jehovah has provided a twenty-first century miracle - he has moved the hearts of "worldly people" who are fit only for destruction to provide the life-sustaining blood fractions that may be needed by his named people.
Furthermore, Jehovah has his angelic medical team protecting that "worldly" blood so that His people do not risk demonic possession by consuming theocratically-approved blood fractions, as they might had they instead purchased a table lamp from a garage sale held by that same worldly person.
Praise Jah, you sheeple!