Dziwisz received the blood from papal doctors when the dying pope, Karol Wojtyla of Poland, underwent a battery of medical tests before a tracheotomy, Polskie Radio reported Monday. The pope, who died in April 2005, led the world's Catholics for 26 of his 84 years.
Dziwisz was advised by Joaquin Navarro-Vals, the spokesman of the Vatican at the time, to retain the blood sample.
The ampoule of blood will become the primary religious relic of John Paul II when he is beatified May 1, Polskie Radio reported.
It will be enclosed in a crystal and placed in an altar at Krakow's John Paul II Institute.
"The practice [of relics] was adopted in the Middle Ages, when many people were illiterate and their knowledge of the world was influenced by magic," said Jesuit priest Krzysztof Madel.
Dziwisz said relics direct people to God, but said he does not want John Paul II's body despoiled for relics.