This disclosure relates generally to a system and method for noninvasive, non-destructive fluorescent measurement. More specifically, the disclosure provides a non-invasive metrology system and method to monitor levels of fluorescent chemicals in the blood. A major application for the invention is field-based non-invasive blood testing for micro-nutrient deficiency and diseases resulting from it, such as Iron deficient anemia. The invention may help reduce or eliminate the need for blood drawing, sending the sample to a blood lab and having to wait for a result.