Mercury has been measured in Danish medieval bones interred at several cemeteries. Bone diagenesis is estimated to play an insignificant role based on measurements of soil samples taken vertically and horizontally away from the thighbone at three graves. Our study shows that mercury-containing medicine has been administered in 79% of the leprosy cases and 40% of the syphilis cases. A substantial number of the monks interred in the cloister walk of the Cistercian Abbey at Øm show heavily increased mercury levels, whereas none of the friars interred in the Franciscan Friary of Svendborg show elevated mercury concentrations. This is interpreted as originating either from exposure to mercury-containing red ink in the scriptorium of the Abbey, or perhaps slightly more likely, from preparing or administering mercury-containing medicine in the hospital of the Abbey.