If donating a vital organ is going to cause death or irreversible harm to the donor, it is morally illicit according to the natural moral law and Catholic social teaching.
According to the Catechism of the Catholic Church, “organ transplants are in conformity with the moral law if the physical and psychological dangers and risks incurred by the donor are proportionate to the good sought for the recipient” (CCC 2296). Donating organs after death is a noble, generous act, provided that the donor or those who have legitimate authority to speak on his or her behalf give explicit consent.
“A vital principle we need to begin with is that the human person must be treated as an end.”
For organ donation to be ethical, whether for a vital or non-vital organ, it must respect the human person as an end—never a means—and requires the donor’s full consent. Organ donation can be a beautiful act of charity if done in accordance with God’s will: informed consent is present and the donation does not cause irreversible damage or death to the donor.