If a donor is between 18 and 60 years old (in special circumstances), a family member, parent, brother or sister, grandparent, or spouse can become a voluntary kidney contributor. For a donor to be compatible, the matched blood group is also necessary. Donor-recipient ABO incompatibility is based on special circumstances, though it is possible to perform such transplants as well. It must be ensured that the donor is free of chronic conditions (diabetes mellitus, hypertension, etc.) that affect kidney performance in order to be eligible for organ donation. The donor should have two functioning kidneys. They must have a blood-borne infection, such as Hepatitis B, Hepatitis C, or Human Immunodeficiency Virus, and they should be in a sufficiently satisfactory mental state to prepare to decide on kidney donations voluntarily.