A transplant is a medical procedure that replaces a damaged or failing organ or tissue with a healthy one, typically from another person. It is often the best, and sometimes the only, treatment for people whose organs have permanently stopped working. More than 100,000 people in the United States are currently on the waiting list for a transplant, and that number grows every year.
What Can Be Transplanted
The kidney is the most commonly transplanted organ, followed by the liver, heart, lungs, pancreas, and intestines. Each of these transplants addresses end-stage organ disease, meaning the organ has failed beyond any other treatment option.
Beyond whole organs, many tissues can also be transplanted. Corneas restore sight lost to injury or infection. Donated skin serves as grafts for burn victims. Bone transplants can replace cancerous sections and prevent amputation. Donated veins are used in heart bypass surgery. A single deceased donor can provide organs and tissues that help dozens of people.
Living vs. Deceased Donors
Organs come from two sources: living donors and deceased donors. A living person can donate one kidney (since you can live with one) or a portion of their liver, which regenerates in both the donor and recipient. Living donation accounts for a significant share of kidney transplants and is growing for liver transplants as well.
Living donors must meet specific criteria. For liver donation, for example, donors need to be between 18 and 60, have a BMI under 32, share a compatible blood type with the recipient, and be free of significant organ disease, cancer, hepatitis, or active infections. Mental health screening and a strong support system for recovery are also required. The donation must be completely voluntary, with no financial compensation or pressure involved.
Deceased donors are individuals who have died, often from brain death due to stroke or trauma, and whose organs remain viable for transplant. One deceased donor can provide up to eight organs.
How Donor Matching Works
Your immune system treats a transplanted organ the same way it treats a virus or bacteria: as a foreign invader. Proteins on the surface of cells, called antigens, act like identity tags. If the antigens on a donated organ don’t match yours closely enough, your body will attack it. That’s why matching donors and recipients is critical.
The matching process looks at two main factors. First is blood type compatibility, which works the same way as a blood transfusion. If you have type B blood, receiving an organ from a type A donor would trigger a dangerous reaction. Second is a set of genetic markers on your cells that determine how your immune system identifies “self” versus “foreign.” The closer these markers align between donor and recipient, the lower the risk of rejection. Doctors also screen the recipient’s blood for pre-existing antibodies that might react against a specific donor’s tissue, and avoid those donors when possible.
The Waiting List and Evaluation Process
Getting on the transplant waiting list isn’t automatic. You need to be evaluated and accepted by a transplant program. You can contact a transplant center yourself; a doctor’s referral isn’t strictly required, though having your medical records available speeds things up. For kidney patients, the ideal time to start evaluation is before the organ fails completely.
The evaluation involves extensive testing: organ function, screening for other diseases, blood work, and immune system marker testing to determine compatibility with future donors. If accepted, you’re placed on the national waiting list managed by the Organ Procurement and Transplantation Network. Of the roughly 108,000 people on that list in the U.S., about 61,000 are active candidates, meaning they are medically ready to receive a transplant at any time. The rest may be temporarily inactive due to health changes or other factors.
Wait times vary dramatically by organ. Kidney patients wait a median of about 384 days. Lung patients now wait a median of 51 days, a major improvement from decades past. Liver and heart patients fall somewhere in between. During the wait, the transplant team periodically repeats tests to make sure you’re still a suitable candidate.
What Happens After a Transplant
Once a transplant is performed, the biggest ongoing challenge is rejection. There are three types, each on a different timeline. The first, hyperacute rejection, happens within minutes if the organ is completely incompatible (such as a blood type mismatch). This is rare today because of pre-transplant testing. Acute rejection can occur anytime from the first week to about three months after surgery. Nearly all recipients experience some degree of it. Chronic rejection is a slow process that unfolds over years, as the immune system gradually damages the transplanted organ.
To prevent rejection, transplant recipients take immune-suppressing medications for the rest of their lives. The standard approach combines three types of drugs: one that blocks a key immune signaling pathway, one that prevents immune cells from multiplying, and a steroid that broadly reduces inflammation. These medications are effective but come with trade-offs. A suppressed immune system means higher susceptibility to infections and, over the long term, a modestly increased risk of certain cancers. Doctors adjust dosages over time, aiming for the lowest effective level.
How Long Transplanted Organs Last
Transplant outcomes have improved enormously over the past few decades. What was once experimental is now a routine, life-saving procedure. Survival rates depend on the organ and the recipient’s overall health.
Lung transplantation has seen some of the most dramatic progress, with median survival reaching 6.7 years for patients transplanted between 2010 and 2017. Wait times for lungs have also dropped sharply: over 73% of listed lung patients now receive a transplant within one year, compared to just 33% in the 1990s. Kidney, liver, and heart transplants have similarly seen steady improvements in both access and long-term outcomes, though each organ carries its own set of risks and recovery timelines.
Pig Organs and the Transplant Shortage
The gap between available organs and the people who need them has driven research into alternatives, including xenotransplantation: using organs from genetically modified animals, primarily pigs. In a recent case published in the New England Journal of Medicine, a 62-year-old man with kidney failure received a gene-edited pig kidney with 69 genetic modifications designed to make it compatible with the human body. The kidney worked immediately, his blood markers improved, and he no longer needed dialysis. He experienced one rejection episode on day 8, which was reversed with medication. He ultimately died on day 52 from pre-existing severe heart disease, unrelated to the transplant itself, and autopsy showed no signs of kidney rejection.
This kind of xenotransplantation remains experimental, but it represents a potential path toward eliminating the organ shortage entirely. Bioengineered tissues and lab-grown organs are also areas of active development, though none are close to routine clinical use.