Tacrolimus Pharmacokinetic Subpopulations

Inclusion Criteria: * Kidney transplant patients at the CHUGA, CHU Saint-Etienne or CHU Clermont-Ferrand, whose new transplant is no more than 7 days old (inclusive) * Patients initially treated with tacrolimus as an immunosuppressant, combined with mycophenolate (MMF), mycophenolic acid (MPA) or everolimus (EVR), with or without corticotherapy. * No plans to remove tacrolimus from the patient's immunosuppressive treatment (e.g. no plans to switch to belatacept a priori), during the first 4 years post-transplantation. * Affiliation to or beneficiary of a social security scheme * Able to read and understand the terms of the protocol * Informed consent obtained, including specific consent for genetic analysis of target genes. * For women of childbearing potential, presence of effective contraception (already acquired for patients treated with mycophenolic acid as an immunosuppressant). Exclusion Criteria: * Contraindication to the use of tacrolimus * Patient already treated with tacrolimus at the time of transplantation * Pregnant, parturient or breastfeeding women * Patient deprived of liberty by judicial or administrative decision * Patient under guardianship or curatorship, or receiving forced psychiatric care * Person admitted to a health or social institution * Subject cannot be contacted in case of emergency * Subject in period of exclusion from another study