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Hemoglobin A1c Testing: The 3-Month Test

The hemoglobin A1c test (also called the A1c test) is a measure of the average blood sugar level over the previous 3 months. This means it can tell us whether the overall blood sugar control is good even though there may be daily changes. This test is also known as the glycosylated or glycated hemoglobin or glycohemoglobin.

Hemoglobin is part of the red blood cell. It carries oxygen from the lungs to the rest of the body. Scientists have discovered that in all people, whether they have diabetes or not, some sugar sticks to the hemoglobin. It stays there for the lifespan of the red blood cell, which is about 3 to 4 months. The amount of sugar that sticks to the hemoglobin reflects the average blood sugar level during that period. It can be measured in a laboratory using the HbA1c test.

Hemoglobin A1c
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Blood sugar measured in mmol/l does not translate directly into the same amount % of HBA1c. If the test shows a result of 11 mmol/L the average blood sugar level percentage HbA1c is actually 9%, not 11%. Keep this in mind when test results are in.
When the average blood sugar level has been high, the A1c result will be high. In this way, the A1c test shows the level of control over the previous few months. The level of A1c achieved over time is the best way we can predict the risk of long-term diabetes-related complications, such as eye, kidney, or nerve damage.

A1c can be measured at any time. Often blood can be collected for this test from a finger prick, but sometimes it has to be taken from a vein. There are different methods for measuring A1c. Some give immediate results. Others take a day or more. 

What is a good A1c reading?

A1c in people without diabetes is about 4% to 6% (0.04 to 0.06). Check the non-diabetic range for your laboratory. Even with intensive treatment, few children and teens with diabetes can reach this level without the risk of having low blood sugar reactions often. Instead, try to achieve the best A1c levels possible. 

For a child with diabetes who does not have many low blood sugar reactions, the following are considered target A1c levels according to the Canadian Diabetes Association Clinical Practice Guidelines (2008):

Age group

Target hemoglobin A1c level

Adults and teens 13 years or older

7.0% or less indicates excellent control

Children aged 6 to 12 years 

Less than 8.0%

Children aged 5 years or under

Less than 8.5%

Levels between 8% and 10% suggest a need for extra effort to improve control. Levels over 10% mean there needs to be a joint, dedicated effort by the child, family, and team to avoid trouble.

Your child should have her A1c measured every 3 months. The results should be recorded to keep track of her overall progress. Be sure to note when a different lab than the usual one processes the test. Different labs can use different methods, which leads to different results. It may give you an inaccurate picture of progress.

Children and teens using insulin pump therapy may be able to aim for lower blood glucose targets and achieve lower A1c levels. Speak with your diabetes team about the best possible targets for your child.

Marcia Frank, RN, MHSc, CDE

Denis Daneman, MB, BCh, FRCPC

2/12/2010

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