Priority for liver transplantation is based on the Model for Endstage Liver Disease (MELD) score, a mathematical function which includes international normalized ratio (INR). We present an analysis to determine the lab-to-lab variation in INR at 14 clinical laboratories across the United States. We performed a survey to identify representative clinical laboratories across the United States, where INR was measured in the determination of MELD score. Five ‘standard’ samples for INR were formulated and were sent to the 14 clinical laboratories to determine variation in INR and MELD score. Among the 14 clinical laboratories, the range in INR for the five samples was: sample 1 (1.2–2.0), sample 2 (1.4–2.5), sample 3 (1.7–3.4), sample 4 (1.9–3.7) and sample 5 (2.4–5.1). The range in calculated MELD score was: sample 1 (8–14), sample 2 (10–17), sample 3 (12–20), sample 4 (14–21) and sample 5 (16–25). The selection of the clinical laboratory used to determine INR may result in substantial changes in MELD score independent of severity-of-illness. These data suggest that further review of interlaboratory variation in MELD should be undertaken because of the potential impact on prioritization for liver transplantation.