A non-invasive method of determining the concentration of an analyte uses Raman spectral information. A high-intensity, narrow band of light (10) is applied to one side (12a) of skin tissue (12). The high-intensity light (10) enters the skin tissue and generates a Raman signal (16). A reflective material (22) is placed in a location nearest the other side (12b) of skin tissue (12). The reflective material (22) is located generally opposite of the entry (A) of the applied high-intensity light (10). The high-intensity light (10) and the Raman signal (20) that pass through the skin tissue (12) are reflected back into the skin tissue (12) via the reflective material (22). The Raman signal (16,20) is collected and the analyte concentration is determined using the collected Raman signal (16,20).