Therapeutic drug monitoring (TDM) is an established strategy to optimize antifungal therapy with certain triazoles. While established relationships exist between concentration and safety or efficacy, the impact of TDM timing on outcomes is unknown. We report clinical outcomes, including antifungal exposure and mortality, in patients receiving institutional versus reference laboratory TDM. The availability of in-house triazole assays reduced the time to drug concentration result (12 versus 68 h; P < 0.001) and time to achieve therapeutic serum concentrations (10 versus 31 days; P < 0.001). Subtherapeutic concentrations were associated with higher patient mortality (32% versus 13.3%; P = 0.036).