In this issue of Pediatric Blood and Cancer, Yim et al. present two articles underscoring the role of anti-Xa levels for optimizing enoxaparin dosing in pediatric patients with obesity. 1,2 Obesity represents a prothrombotic state, akin to an acquired thrombophilia, characterized by alterations in clotting factors, impaired fibrinolysis, and comorbidities such as hypertension, dyslipidemia, diabetes, and metabolic syndrome that increase risk of thrombosis through endothelial activation. In one study, they highlight the necessity of a higher starting dose for venous thromboembolism (VTE) prophylaxis, as evidenced by 53% of patients with a body mass index (BMI) higher than 99th percentile exhibiting subtherapeutic levels. 2 In the second study, they demonstrate that empiric treatment dosing of enoxaparin at 1 mg/kg twice daily resulted in supratherapeutic levels, requiring dose reduction. 1 Both studies