A photo-acoustic sensing apparatus (100) for non-invasive measurement of blood parameters of a subject (102) comprises a photo-acoustic sensor (104) for sensing photo-acoustic signals (106) induced when a region of the subject is illuminated by a light source (108). A first sensor processing module (112) may derive blood oxygen saturation using sensed photo-acoustic signals (114). A second sensor processing module (116) may derive blood core temperature using sensed photo-acoustic signals. A third sensor processing module (118) may derive blood glucose using sensed photo-acoustic signals. The sensing apparatus is configured to derive at least one of: a de-correlated value (120) of blood oxygen saturation of the subject； a de-correlated value (122) of blood core temperature of the subject； and a de-correlated value (124) of blood glucose of the subject.
