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Glycated hemoglobin, also known as glycosylated hemoglobin or Hb1Ac, is a blood test that aims to assess glucose levels in the last three months before the test. That's because glucose is able to stay attached to one of the components of the red blood cell, hemoglobin, throughout the red blood cell cycle, which lasts about 120 days.
Thus, the exam of glycated hemoglobin is requested by the doctor to identify diabetes, monitor its development or check if the treatment of the disease is being effective, being done by analyzing a small sample of blood collected in the laboratory.
What is glycated hemoglobin for
The examination of glycated hemoglobin is done with the aim of assessing glucose levels in recent months, being useful in the diagnosis of diabetes. In addition, in the case of people who have already been diagnosed with diabetes, this test is useful to check if the treatment is being effective or is being done correctly, because if it is not, changes in the result can be verified.
In addition, when the value of glycated hemoglobin is much higher than the normal considered by the laboratory, there is a greater likelihood of the person developing complications related to diabetes, such as cardiac, renal or neuronal changes, for example. See what are the main complications of diabetes.
This test is more suitable than fasting glucose for the initial diagnosis of diabetes, because the glucose test can be influenced by changes in recent eating habits, not representing the circulating sugar levels in recent months. Thus, it is possible that before carrying out the glucose test, the person has a healthier diet and low in sugar, so that the fasting glucose may be within normal values, which may not represent the person's reality.
Thus, in order to diagnose diabetes, fasting glucose, glycated hemoglobin and / or the glucose tolerance test, TOTG, are normally requested. Learn more about the tests that help diagnose diabetes.
Reference values
The reference values for glycated hemoglobin may vary according to the laboratory, however in general the values considered are:
- Normal: Hb1Ac between 4.7% and 5.6%;
- Pre-diabetes: Hb1Ac between 5.7% and 6.4%;
- Diabetes: Hb1Ac above 6.5% in two tests performed separately.
In addition, in people already diagnosed with diabetes, Hb1Ac values between 6.5% and 7.0% indicate that there is good control of the disease. On the other hand, values above Hb1Ac above 8% indicate that diabetes is not being properly controlled, with a higher risk of complications and a change in treatment is necessary.
The glycated hemoglobin test does not require any preparation, however as it is usually requested together with the fasting glucose test, it may be necessary to fast for at least 8 hours.