<prompt> Glycated haemoglobin reflects blood glucose of preceding0-1 week2-3 week4-5 week6-8 week  <response>: When blood glucose enters the erythrocytes, it glycates the e-amino group of lysyl residues and the amino terminals of haemoglobin.The fraction of haemoglobin glycated, normally about 5, is propoionate to blood glucose concentration.Since the half-life of an erythrocyte is typically 60 days, the level of glycated haemoglobin HbA1c reflects the mean blood glucose concentration over the preceding 6 to 8 weeks. Measurement of HbA1c, therefore, provides valuable information for management of diabetes mellitus.Reference: Harper biochemistry, 30th edition, page no 58 