Abstract: A combined absorption-reflection based instrument and methods are introduced here to measure antioxidant carotenoids and similar compounds such as: beta-carotene, lycopene and lutein, along with others in living human tissue (e.g. skin). The device and methods provide a non-invasive, rapid, accurate, repeatable, safe and reliable method for measuring antioxidant levels in human tissue, providing information that can be used for many diagnostic and/or health purposes.