A portable mains (AC-powered) device intended to be used during intravenous fluid administration to detect and alert healthcare professionals to infiltration/extravasation (leaking of fluid into the surrounding tissues). It includes a display, light source, and a light sensor. Light [visible/near infrared (NIR)] from the monitor is directed to the skin surface near the IV access site, and reflected light from the tissues is directed back to the sensor in the monitor, via a dedicated fibreoptic cable (not included); the monitor is intended to detect changes in reflected light which are processed to indicate fluid leakage.