Based on TPMT status, start with reduced doses (50% to 80% of normal dose) if normal starting dose is ≥ 40-60 mg/m2/day (e.g., 20-48 mg/m2/day) and adjust doses of thioguanine based on degree of myelosuppression and disease-specific guidelines. Allow 2-4 weeks to reach steady-state after each dose adjustment. If myelosuppression occurs, and depending on other therapy, emphasis should be on reducing thioguanine over other agents (PMID 20354201, 11037857). NUDT15 phenotype could not be assigned based on genotyping. If thiopurines are required and NUDT15 status is unknown, monitor closely for toxicity.