Ischemic stroke is a common and severe occurrence in Sickle Cell Anaemia (SCA) but no accurate screening measures currently exist for adults. Changes in venous oxygen saturation (Yv) have been suggested as a potential biomarker but measuring Yv in vivo is challenging. This work explores the potential of MRI susceptibility mapping to measure Yv in SCA subjects. Susceptibility-mapping-based measures of Yv were compared between 25 SCA subjects and 15 healthy controls. Significantly lower Yv was measured in the superior sagittal sinus in the SCA group compared to healthy controls, showing that QSM is sensitive to changes in Yv in SCA.