Objective: The study aims to determine the relationship between the characteristics of Tacrolimus trough concentration (C0 TAC) from month 2 to month 12 after kidney transplantation with some clinical outcomes, thereby initially determining the optimal C0 TAC target for patients after kidney transplantation. Methods: A longitudinal retrospective observational study on 257 living - donor kidney transplant patients. Regression analysis was used to evaluate the relationship between mean and coefficient of variation of C0 TAC during the period from 2 months to 12 months after transplantation with clinical outcomes at 12 months post - transplantation, including eGFR, proteinuria, biopsy - proven acute rejection, acute kidney injury, CMV and PCP infection, hospitalization for non - CMV and PCP infections. Results: Patients with mean C0 TAC <
7 ng/ml had the highest risk of eGFR decline and this risk decreased in patients with higher mean C0 TAC, especially in the C0 TAC ≥ 9 ng/ml group (OR = 0.206
p = 0.001
CI 95%: 0.079 - 0.536). Patients with mean C0 TAC 7 - 7.9 ng/ml had a lower risk of acute kidney injury in the first 12 months after transplantation than the group with C0 TAC <
7 ng/ml (OR = 0.234
p = 0.044). The risk of acute rejection in the first 12 months after transplantation tended to decrease in patients with C0 TAC 7 - 7.9 and 8 - 8.9 ng/ml (ORs are respectively 0.612 and 0.25), the difference is not statistically significant. Patients with mean C0 TAC ≥ 9 ng/ml had a higher risk of CMV infection than patients with C0 TAC <
7 ng/ml (OR = 3.737
p = 0.012). The events of acute kidney injury, acute rejection, and hospitalization for non - CMV and PCP infections were more likely to occur in patients with a higher TAC coefficient of variation (ORs are respectively 1.045, 1.049, 1.044 with p = 0.01
0.049 and 0.001). Conclusion: The optimal treatment target of TAC trough level needs to be considered based on different clinical outcomes. A treatment target of 7 - 8.9 ng/ml may be considered for transplant patients during the period from month 2 to month 12 after kidney transplantation.