In this study, the optical properties of glycated (HbA1c) and nonglycated (Hb) hemoglobin are compared using Surface-enhanced Raman spectroscopy (SERS), spectrofluorimetry, and refractometry. Analysis of the spectral shift of SERS spectra showed good discrimination between two hemoglobins indicating differences in their molecular structure. The fluorescence spectra measured at excitation wavelengths of 260, 270, and 280 nm also indicate differences in the molecular structure of these hemoglobins. For the first time refractive index temperature increments were measured for HbA1c in a wide wavelength range in the visible and NIR as -(1.35 ± 0.11) 10 -4 °C-1 and compared with normal hemoglobin (dn/dT = -(1.02 ± 0.12) 10 -4 °C-1 ). The comparison of temperature RI increments for hemoglobin obtained from the whole blood of healthy volunteers and diabetic patients is also done. The data obtained can serve as a basis for further study of the optical properties of glycated hemoglobin and other glycated proteins.