Glycosylated Hemoglobin A1C
|Why is this test performed?||This test is used to monitor the effectiveness of diabetes treatment over time.|
|How to prepare:||
In adults who do not have diabetes, glycosylated hemoglobin A1C:
In patients with diabetes, glycosylated hemoglobin A1C:
|Related tests:||This test is seldom performed on its own. Blood glucose is usually measured at the same time. Self-monitoring of blood glucose and of ketone bodies in urine and blood are also part of diabetes monitoring.|
Over time, as is the case with a large number of proteins, the hemoglobin molecules in red blood cells become glycosylated (binding to glucose, a type of sugar found in the blood). The amount of glucose-bound hemoglobin is a function of blood glucose levels. In diabetics with high blood glucose levels, a larger percentage of hemoglobin will bind to glucose.
Glycosylated hemoglobin levels, which are used to assess the effectiveness of diabetes therapy, provide us with information about blood glucose control over the past three to four months and are relatively unaffected by short-term changes in glycemia (associated with an infection, temporary use of medication, etc.). This may present an advantage over blood glucose tests. Glycosylated hemoglobin appears to be more accurate in predicting the risk for long-term complications.
Target levels are personalized based on each patient and their hypoglycemia risk. The potential benefits must be weighed against the disadvantages associated with a more intensive treatment. Although a lower target, between 6 and 6,5%, can lower the risk of long-term complications (kidney and eye disease), there is a greater risk for severe hypoglycemia. A higher target (7.1 to 8,5%) can be considered in those with long-standing diabetes, a known history of hypoglycemia, those with advanced complications with their diabetes or with other characteristics. You will find in the table below the relationship between glycosylated hemoglobin and the average blood glucose value.
|Average blood glucose
Adapted from the American Diabetes Association
What does an abnormal test result mean?
If the result is too high
When blood glucose levels are high and diabetes management is suboptimal, glycosylated hemoglobin results may be elevated.
If the result is too low
Levels below 6.0% may indicate an increased incidence of hypoglycemic episodes.
Factors that may alter results:
Because pregnancy can affect glycosylated hemoglobin levels, this test is not performed in women who are pregnant.
Other factors can alter results include:
- A blood disease that destroys or alters red blood cells
- Chronic alcohol ingestion
- Kidney or liver problem
- Iron or B12 deficiency anemia
- Prolonged bleeding
- Recent blood transfusion
- Rheumatoid arthritis
- Splenectomy (removal of the spleen)
- Some medications
What you need to know before the test
Before going for blood tests, a procedure or other exam, it is best to always bring a list of all the drugs you take (prescription, OTC and natural health products). Unless told otherwise, you should take your medication as usual on the day of the test. When in doubt, ask your pharmacist for more information.
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The patient information leaflets are provided by Vigilance Santé Inc. This content is for information purposes only and does not in any manner whatsoever replace the opinion or advice of your health care professional. Always consult a health care professional before making a decision about your medication or treatment.