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How organ allocation works

In the U.S., the demand for organs is far greater than the supply. We don’t have enough donated organs to transplant everyone in need, so we balance factors of:

  • Justice (fair consideration of candidates' circumstances and medical needs)
  • Medical utility (trying to increase the number of transplants performed and the length of time patients and organs survive)

Many factors used to match organs with patients in need are the same for all organs. But the system must factor in some unique differences for each organ.

The matching process

The computer system that matches donors and recipients first filters out any transplant candidates who cannot match the donor. This could be due to a number of factors, including:

  • Blood type match
  • Height or weight
  • Medical facts specific to the organ type (for example, immune system matching for kidney or pancreas)

The computer system then sets the order that candidates will receive offers. National policies address the priority given for each matching factor.

Geography plays a part

Organs can only be used if transplanted within hours of recovery. For this reason, the system gives priority to candidates at transplant hospitals closer to the donor hospital.

The right-sized organ

An organ of matching size is critical to a successful transplant. For example, children often respond better to child-sized organs. In general, children get first consideration for other children's organs.

Factors in organ allocation

Blood type and organ size weigh into the allocation of every donated organ. Other factors are unique to each organ type.


  • Waiting time
  • Level of donor/recipient immune system match
  • Pediatric status
  • Prior living donor
  • Distance from donor hospital
  • Survival benefit


  • Medical urgency
  • Distance from donor hospital


  • Survival benefit
  • Medical urgency
  • Waiting time
  • Distance from donor hospital


  • Medical urgency
  • Distance from donor hospital

Preserving organs

Organs can only be preserved for a fairly short time between removal from the donor and transplant into a recipient. They cannot be frozen and kept in storage for several days or weeks.

Kidneys are usually transplanted within 36 hours after removal from the donor. The liver, pancreas, and intestinal organs are typically transplanted within 12 hours. Hearts and lungs have the shortest preservation time; they are usually transplanted within six hours.

Transplant teams prefer the shortest possible preservation time, to offer the best chance of a successful transplant. Each team uses its own medical judgment in deciding on a time limit for preservation. Even so, there are commonly accepted ranges based on the organ type.