Based on NUDT15 status, start with reduced starting doses (30%-80% of normal dose) if normal starting dose is 2-3 mg/kg/day (e.g., 0.6 – 2.4 mg/kg/day), and adjust doses of azathioprine based on degree of myelosuppression and disease-specific guidelines. Allow 2-4 weeks to reach steady-state after each dose adjustment (PMID 20354201, 11302950, 15606506, 16530532). TPMT phenotype could not be assigned based on genotyping performed. Consider evaluating erythrocyte TPMT activity to assess TPMT phenotype. If thiopurines are required and TPMT status is unknown, monitor closely for toxicity.