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Background and Importance Linezolid is an antibiotic indicated for severe infections, but its high pharmacokinetic variability may compromise both efficacy and safety. Therapeutic drug monitoring (TDM) can optimise dosing and reduce the risk of adverse effects.Aim and Objectives To analyse the use of linezolid in hospitalised patients and assess the proportion of prescriptions meeting criteria for TDM, based on the expert consensus statement on Exper consensus statement on therapeutic drug monitoring and individualisation of linezolid (doi: 10.3389/fpubh.2022.967311).Material and Methods Retrospective observational study in a tertiary hospital including all patients prescribed linezolid from January to March 2025. Data were obtained from the hospital’s electronic prescribing system.Collected variables included demographics (sex, age), clinical data (route of administration, treatment duration), and TDM criteria: critical illness, paediatrics (<12 years), renal impairment (eGFR <60 mL/min), hepatic impairment (AST/ALT >5×ULN), elderly (>75 years), obesity (BMI >30 kg/m2), or drug interactions (clarithromycin, proton pump inhibitors, amiodarone, amlodipine, calcium channel blockers, rifampicin, phenobarbital, levothyroxine). Prescriptions were classified according to the presence of one or more TDM criteria.Results A total of 236 patients were included (70% male, median age 73 [1-99] years), with 266 prescriptions (83% intravenous, 17% oral). The median treatment duration was 7 [3-26] days; prescriptions ≤2 days were excluded due to lack of steady-state achievement. TDM criteria were met in 99% of prescriptions. The most frequent criterion was drug interaction (35%), mainly with proton pump inhibitors, followed by amlodipine, levothyroxine, and amiodarone; however, most were low risk. Rifampicin was identified in 1% of cases and was the only interaction significantly reducing linezolid levels. Additional TDM criteria were: elderly patients (16%), critically ill (16%), renal impairment (16%), obese (12%), hepatic impairment (2%), and paediatric (2%).Conclusion and Relevance Nearly all linezolid prescriptions met at least one criterion for TDM, with around 60% involving factors that significantly affect pharmacokinetics. These findings support the need for implementing standardised TDM protocols to ensure safe and effective use of linezolid in clinical practice.Conflict of Interest No conflict of interest