Petri M, Konig MF, Li J, et al. - This research sought to evaluate the utility of hydroxychloroquine (HCQ) blood monitoring in predicting thrombosis risk in a longitudinal systemic lupus erythematosus (SLE) cohort. In this study, t‐tests between patients with and those without thrombosis were used to compare the mean HCQ blood levels calculated prior to thrombosis or until the last visit. Rates of thrombosis and HCQ blood level were examined by using pooled logistic regression. Researchers estimated rate ratios and 95% confidence intervals (95% CIs). Thrombosis occurred in 38 patients (5.1%) among 739 patients with SLE. The outcomes indicate that in SLE, low HCQ blood levels are correlated with thrombotic events. As per the findings, the longitudinal assessment of HCQ levels may allow for personalized HCQ dosing strategies. In this high‐risk population, recommendations for empirical dose reduction may decrease or eliminate the benefits of HCQ.