Molecular model of glycosylated (or glycated) hemoglobin (hemoglobin A1c, or HbA1c), a form of hemoglobin used primarily to identify the average plasma glucose concentration over prolonged periods of time. In this rendering of the structure, based upon the Protein Database (PDB) entry 3B75, the sugar molecules are shown as space-filling spheres with their carbon atoms blue and the oxygens red, the heme groups are shown as blue planar structures and the oxygens associated with the hemes are shown as red spheres. The protein backbone of the hemoglobin is shown in yellow and purple as a ribbon.