Type 2 diabetics should have the HbA1c test carried out; the HbA1c level indicates what the average blood sugar levels have been over the past two to three months.
If you are not having this test carried out every three to six months, you should be talking to your doctor.
Glycosylated hemoglobin, abbreviated HbA1c, is used to evaluate blood sugar control because it gives a more long-range picture than a blood sugar level taken on any given morning.
Hemoglobin is a molecule found in red blood cells.
It is the molecule that carries oxygen throughout your body.
Red blood cells live for about 120 days, so by measuring the glucose in hemoglobin we can get a picture of what the blood sugar has been for about the past three months.
Different hemoglobin molecules: Most human hemoglobin molecules are the same, but hemoglobin is a large molecule, and some people have hemoglobin molecules that are slightly different from the usual kind.
The molecule is made up of amino acids and iron ions.
There are more than 20 kinds of amino acids, and occasionally someone is born with a different amino acid in place of a customary one.
One such substitution causes sickle cell anemia...

• while normal human hemoglobin is abbreviated HbA, the sickle cell hemoglobin is abbreviated HbS.
  

While a normal molecule of hemoglobin has an amino acid called glutamic acid among its many amino acids, a hemoglobin molecule in sickle cell anemia has another amino acid, valine, in the same position.
Another variation is HbF, a hemoglobin molecule that is the same as the hemoglobin made by fetuses, but occasionally seen in adults.
In that variation there are more than one amino acid substitution.
Variants such as HbS and HbF are termed hemoglobinopathies.
Hemoglobinopaties: According to research performed in the Department of Biochemistry and Clinical Chemistry, Faculty of Medicine, University of Kelaniya, Ragama, Sri Lanka, testing for HbA1c in patients with HbS or HbF can give false results.
Results of their study were published in September, 2010 in the Southeast Asian Journal of Tropical Medicine and Public Health.
Two thousand six hundred and ninety-five diabetic patients were tested for hemoglobinopathies.
Two per cent were found to have HbF or HbS.
HbA1c levels in patients with normal hemoglobin are a better indication of blood sugar than the same measurements taken in patients with hemoglobinopathies HbF or HbS.
The researchers concluded that diabetics with HbA1c levels that appear not to be correlated with fasting blood sugar levels should be tested for hemoglobinopathies.
Frequencies of hemoglobinopathies vary widely in different populations.
One study in southern Turkey found hemoglobin S in:

• 3.
  9 per cent of the overall population
• 9.
  6 per cent in Arabic people, while
• none was seen in Kurds.
  

Another study performed in Brazil found 14 per cent of people in certain regions carrying the sickle cell trait, while in other regions there were no carriers.
If fasting blood sugar levels consistently tell a different story from the HbA1c test results, consider discussing the possibility of a hemoglobinopathy with your doctor.