Sheikh Ahmad Kutty, a senior lecturer and Islamic scholar at the Islamic Institute of Toronto, Ontario, Canada , states: “Organ donation is perfectly Islamic as long as it is done in compliance with certain conditions. The following are the conditions scholars have stipulated for donation:
Conditions associated with a living donor:
1. He/she must be a person who is in full possession of his/her faculties so that he/she is able to make a sound decision by himself/herself;
2. He/she must be an adult and, preferably, at least twenty-one years old;
3. It should be done on his/her own free will without any external pressure exerted on him/ her;
4. The organ he/she is donating must not be a vital organ on which his/her survival or sound health is dependent upon;
5. No transplantation of sexual organs is allowed.
Conditions associated with deceased donors:
1. It must be done after having ascertained the free consent of the donor prior to his /her death. It can be through a will to that effect, or signing the donor card, etc.
2. In a case where organ donation consent was not given prior to a donor’s death, the consent may be granted by the deceased’s closest relatives who are in a position to make such decisions on his/her behalf.
3. It must be an organ or tissue that is medically determined to be able to save the life or maintain the quality of life of another human being.
4. The organ must be removed only from the deceased person after the death has been ascertained through reliable medical procedures.
5. Organs can also be harvested from the victims of traffic accidents if their identities are unknown, but it must be done only following the valid decree of a judge.
as for the last part of your question, you are certainly allowed to sign a Donation Card as long as the stated conditions are met.“