OBJECTIVES: Our economic evaluation of warfarin pharmacogenetic (PGx) test revealed that the test was not cost-effective in Thailand, based on input parameters derived from a meta-analysis of Caucasians-dominant studies for the relative risk (RR) of major bleeding in variant genotypes of CYP2C9 [2.19, 95%CI (1.33-3.60)] and VKORC1 [1.08, 95%CI (0.55-2.10)]. Considering this limitation and the high prevalence of VKORC1 variant genotype in Thailand, this study aimed to determine the threshold value of the RR of major bleeding for VKORC1 variant genotypes leading PGx test to be  cost-effective. METHODS: We conducted a literature search for local and international publications investigating the relationship of VKORC1 genotype and the risk of major bleeding in warfarin users. Additionally, interviews with local key cardiologists were undertaken. A threshold analysis was performed for patients aged 45 years old using the previously constructed decision analytic model. The model was populated from the societal perspective. Input data were obtained from literature review, meta-analysis, and electronic hospital database analyses. Incremental cost-effectiveness ratios (ICERs) were presented as year 2013 values. RESULTS: Literature search and interviews identified no local evidence on the relationship of VKORC1 genotype and the RR of major bleeding in warfarin users. In base-case analysis, PGx results in 0.00198 QALY gained, and increases costs by 2,953.23 THB (98.44 USD) compared with UC (ICER 1,494,707.9 THB [49,823 USD] per QALY gained). In order for the PGx test to be cost-effective, the RR for major bleeding in VKORC1 variant genotype needs to be shifted from 1.08 (base-case) to 4.15. CONCLUSIONS: Our finding suggests that PGx-guided warfarin dosing is not a cost-effective intervention in Thailand due to low likelihood of the RR for major bleeding in VKORC1 variant genotype to be as high as 4.15. This evidence can be used to assist policy makers and clinicians in efficiently allocating limited resources.