Hemoglobin (Hb) within single erythrocytes (red blood cells), adsorbed on poly-lysine coated glass surfaces, was studied using resonance Raman spectroscopy and global Raman imaging. The erythrocytes were found to be sensitive to both surface adsorption and to the laser light. Topological changes of the cell membrane were observed immediately after cell adsorption in Raman images. We observed a photo-induced increase of the fluorescence background occurring simultaneously with a decrease in the Hb Raman signal. Concurrent changes in Raman spectra revealed a conversion of oxy-Hb to the met-Hb state. However, at a low accumulated photon dose, the preparation method enabled the recording of Raman spectra during the oxygenation cycle of a single red blood cell in buffer, which shows that Hb was in an in-vivo environment. Thus, Raman spectroscopy of functional Hb in isolated red blood cells is feasible.