Understanding Organ Transplant Waiting Lists

The National Organ Allocation System

The United Network for Organ Sharing (UNOS) administers the national transplant waiting list under a federal contract with the Health Resources and Services Administration (HRSA). When a patient needs a transplant, their transplant center lists them with UNOS. There is one centralized waiting list, not separate lists per center, though patients can be listed at multiple centers simultaneously (a practice called "multiple listing").

As of SRTR data through November 2025, approximately 100,000+ people are waiting for organ transplants in the United States at any given time. The kidney waiting list is by far the largest, accounting for over 80% of all candidates. See our organ overview pages for current waitlist numbers by organ type.

How Organ Allocation Actually Works

When an organ becomes available, typically from a deceased donor, the Organ Procurement Organization (OPO) enters the donor information into the UNOS computer system. The matching software generates a ranked list of potential recipients based on multiple factors:

• Medical urgency: Sicker patients generally rank higher. For liver transplants, the MELD (Model for End-Stage Liver Disease) score is the primary ranking criterion. For heart transplants, status categories from 1-6 determine priority.
• Blood type and tissue compatibility: The organ must be biologically compatible. ABO blood type matching is mandatory for most organs.
• Geographic proximity: Organs have limited preservation time (4-6 hours for hearts, up to 24 hours for kidneys). Local and regional candidates are prioritized before national.
• Wait time: Used as a tiebreaker when multiple candidates have similar medical urgency and compatibility. Longer wait equals higher priority.
• Pediatric priority: Organs from pediatric donors are prioritized for pediatric recipients.
• Body size: Particularly important for hearts and lungs, where donor-recipient size matching affects outcomes.

Wait Time Variability: What the Data Shows

Median wait times vary dramatically by organ type, blood type, geographic region, and the patient's medical urgency at listing. National averages mask enormous local variation.

Kidney: The longest waits, median 3 to 5 years nationally, but some regions exceed 7 years. Living donor transplants bypass the deceased-donor waiting list entirely and are the fastest path to transplant.

Liver: Allocated primarily by MELD score rather than wait time. Patients with higher MELD scores (indicating more severe liver disease) receive organs faster, sometimes within weeks. Lower-MELD patients may wait years or never reach transplant.

Heart: Status-based allocation means the sickest patients (Status 1-2) often receive organs within weeks to months. Stable outpatients may wait significantly longer.

Blood type O candidates face longer waits across all organ types because O organs can be transplanted into any blood type (universal donor for some organs), reducing the available supply for O recipients.

Multiple Listing: Being on More Than One List

Patients can be listed at multiple transplant centers in different regions. This is legal, common, and can meaningfully reduce wait times, especially for kidney transplants where regional variation in wait times is extreme. A patient listed in both a high-wait region (like parts of California or the Northeast) and a lower-wait region (like parts of the South or Midwest) may receive an offer years sooner.

The trade-off: each center requires its own medical evaluation, you must be able to travel to the center quickly when an organ becomes available (typically within hours), and insurance coverage varies. Browse our transplant center directory to compare programs across regions.

Frequently Asked Questions