NUDT15 emerges as a prominent predictive genetic marker associated with thiopurine tolerance specifically within the Asian population. The variant NUDT15 stands out as a prevalent mutation known to trigger severe myelosuppression and hair loss, necessitating a reduction in dosage for affected patients. Nevertheless, the clinical relevance of less common variants remains largely unexplored to date. The varied functional impacts are anticipated to be contingent upon the specific alleles of NUDT15, suggesting that discerning the NUDT15 diplotype could pave the way for a more personalized approach to thiopurine therapy, tailored to individual patient requirements. It is imperative to conduct further investigations to assess the practical clinical implications of utilizing preemptive NUDT15 genotyping as a basis for determining the initial dosage of thiopurine, with a focus on the forthcoming decade.