Glycosylated (or glycated) hemoglobin (hemoglobin A1c, Hb_1c , Hb_A1c or Hg_A1c) is a form of hemoglobin used primarily to identify the plasma glucose concentration over time. Its name is sometimes abbreviated to A1C. 3-dimensional structure of hemoglobin. ... Blood plasma is the liquid component of blood, in which the blood cells are suspended. ... Glucose (Glc), a monosaccharide (or simple sugar), is one of the most important carbohydrates. ... In chemistry, concentration is the measure of how much of a given substance there is mixed with another substance. ...

Underlying principle

In the normal 120-day life span of the red blood cell, glucose molecules join hemoglobin, forming glycated hemoglobin. In individuals with poorly controlled diabetes, increases in the quantities of these glycated hemoglobins are noted. Human red blood cells Red blood cells are the most common type of blood cell and are the vertebrate bodys principal means of delivering oxygen from the lungs or gills to body tissues via the blood. ... Glycation is the result of a sugar-reducing molecule, such as fructose or glucose, bonding to a protein or lipid molecule without the controlling action of an enzyme. ... This article is about the disease that features high blood sugar. ...

Once a hemoglobin molecule is glycated, it remains that way. A buildup of glycated hemoglobin within the red cell reflects the average level of glucose to which the cell has been exposed during its life cycle. Measuring glycated hemoglobin assesses the effectiveness of therapy by monitoring long-term serum glucose regulation. The Hb_A1c level is proportional to average blood glucose concentration over the previous four weeks to three months (some researches state that the major proportion of its value is related to a rather short term period of two to four weeks [1]). A life cycle includes the major sexual stages of a species, especially in regard to its ploidy. ...

Interpretation of results

The normal range (that found in healthy persons) is 4% to 5.9%.[2]. People with diabetes mellitus often have higher levels of Hb_A1c. While diabetic patient treatment goals vary, many include a target range of Hb_A1c values. A diabetic with good glucose control has a Hb_A1c level that is close to or within the reference range. The International Diabetes Federation and American College of Endocrinology recommends Hb_A1c values below 6.5%, while the range recommended by the American Diabetes Association extends to 7%. A very high Hb_A1c represents poor glucose control. For the disease characterized by excretion of large amounts of severely diluted urine, see diabetes insipidus. ... In health-related fields, a reference range is a set of values of some measurement that a physician or other health professional can use to interpret a set of results for a particular patient. ... The American Diabetes Association, or the ADA, is an American health organization providing diabetes research, information and advocacy. ...

Interpreting results is somewhat difficult because (1) laboratory results can differ depending on the analytical technique and (2) biological variation between individuals can be up to 1% (i.e. two individuals with the same average blood sugar can have A1C values that differ by up to 1%).

The mapping between Hb_A1c and blood glucose average is shown in the table below.

Contraindications to use of test

Glycated hemoglobin measurement is not appropriate where there has been a recent change in diet or treatment within 6 weeks. Likewise the test assumes a normal red blood cell aging process and mix of haemoglobin subtypes (predominantly HbA in normal adults). Hence people with recent blood loss or hemolytic anemia, or hemoglobinopathy such as sickle cell disease are not suitable for this test. The alternative fructosamine test may be used in these circumstances and it similarly reflects an average of blood glucose levels over the preceding 2 to 3 weeks. Hemolytic anemia is anemia due to hemolysis, the abnormal breakdown of red blood cells either in the blood vessels (intravascular hemolysis) or elsewhere in the body (extravascular). ... Hemoglobinopathy is a kind of genetic defect that results in abnormal structure of one of the globin chains of the hemoglobin molecule. ... ... Fructosamine, also known as Glycated Serum Protein (GSP) or Glycated Albumin, is used primarily to identify the plasma glucose concentration over time and so assess diabetic control . ...

References

• Hemoglobin A1c Test
• The Glycated Hemoglobin Test
• MDRTC Hemoglobin A1C Fact Sheet

See also

• Diabetes mellitus
• Hemoglobin