The hemoglobin A1c test, also called HbA1c, glycated hemoglobin test, or glycohemoglobin, is an important blood test that shows how well your diabetes is being controlled. Formation of Glycosylated hemoglobin is essentially irreversible and the blood levels depend on both the life span of red blood cell (average 120 days) and blood glucose concentration. Once glucose attaches to haemoglobin, it doesn't let it go. It's there for the lifetime of the red blood cell, which, in total is several months as new red blood cells are continually being made and others are dying. All this means that a glycohemoglobin test shows your average blood glucose level over the previous 6-8 weeks. It is therefore called a test with memory. Therefore, they represent integrated values for glucose over the preceding six to eight weeks. Increased synthesis of haemoglobin A1c correlates with lack of glucose control; in diabetics with good glucose control, the amount of Haemoglobin A1c returns to the reference levels. The HbA1c test should be done every three to six months, depending on the treatment program and level of control of diabetes.The ADA recommends that the HbA1c level first are measured at the time of diagnosis and initiation of treatment. Thereafter, the test should be done at least twice a year in people with non-insulin-dependent (type II) diabetes who do not use insulin; four times a year in people with insulin-dependent (type I) diabetes or those with type II diabetes who use insulin.