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A glycohemoglobin test, or hemoglobin A1c, is a blood test that checks the amount of sugar (glucose) bound to the hemoglobin in the red blood cells. People who have diabetes or other conditions that increase their blood glucose levels have more glycohemoglobin (sugar bound to hemoglobin) than normal.
An A1c test can be used to diagnose prediabetes or diabetes. The A1c test checks the long-term control of blood glucose levels in people with diabetes. Most doctors think checking an A1c level is the best way to check how well a person is controlling his or her diabetes. This test can be done with a blood draw from a vein. Sometimes an A1c test can be done with blood from a finger stick.
A home blood glucose test measures the level of blood glucose only at that moment. Blood glucose levels change during the day for many reasons, including medicine, diet, exercise, and the level of insulin in the blood.
It is useful for a person who has diabetes to have information about the long-term control of blood sugar levels. The A1c test result does not change with any recent changes in diet, exercise, or medicines.
Glucose binds to hemoglobin in red blood cells at a steady rate. Since red blood cells last 3 to 4 months, the A1c test shows how much glucose is in the plasma part of blood. This test shows how well your diabetes has been controlled in the last 2 to 3 months and whether your diabetes treatment plan needs to be changed.
The A1c test can also help your doctor see how big your risk is of developing problems from diabetes, such as kidney failure, vision problems, and leg or foot numbness. Keeping your A1c level in your target range can lower your chance for problems.
This test is done to:
You do not need to stop eating before you have an A1c test. This test can be done any time during the day, even after a meal.
The health professional taking a sample of your blood will:
The blood sample is taken from a vein in your arm. An elastic band is wrapped around your upper arm. It may feel tight. You may feel nothing at all from the needle, or you may feel a quick sting or pinch.
There is very little chance of a problem from having blood sample taken from a vein.
A1c is a blood test that checks the amount of sugar (glucose) bound to hemoglobin. The result is shown as a percentage. The result of your A1c test can also be used to estimate your average blood sugar level. This is called your estimated average glucose, or eAG. Your doctor will have your test results in a few days.
The criteria from Diabetes Canada used to diagnose diabetes includes the option of testing A1c. Your doctor may repeat the test to confirm the diagnosis of diabetes.
Each lab has a different range for what's normal. Your lab report should show the range that your lab uses for each test. The normal range is just a guide. Your doctor will also look at your results based on your age, health, and other factors. A value that isn't in the normal range may still be normal for you.
Less than 6.0%
Prediabetes (increased risk for diabetes)
6.5% and higher
Diabetes Canada recommends that most non-pregnant adults who have diabetes and children who have type 2 diabetes have an A1c level of 7.0%. There is evidence to suggest that for children with type 2 diabetes, having an A1c of <6.0% within the first 6 months of diagnosis may reduce the risk of treatment failure. Diabetes Canada recommends that most children who have type 1 diabetes have an A1c level of 7.5% or less. Talk to your doctor about your diabetes treatment plan and your target A1c goal.
Estimated average plasma glucose ( mmol/L)
Some medical conditions can increase A1c levels, but the results may still be within a normal range. These conditions include Cushing's syndrome, pheochromocytoma, and polycystic ovary syndrome (PCOS).
Corticosteroid treatment increases the A1c level.
Reasons you may not be able to have the test or why the results may not be helpful include:
CitationsDiabetes Canada Clinical Practice Guidelines Expert Committee, et al. (2018). Definition, classification and diagnosis of diabetes, prediabetes and metabolic syndrome. Canadian Journal of Diabetes, 42(Suppl 1): S10–S15. DOI: 10.1016/j.jcjd.2017.10.003. Accessed October 15, 2018.American Diabetes Association (2019). Standards of medical care in diabetes—2019. Diabetes Care, 42(Suppl 1): S1–S193. Accessed December 17, 2018.
Adaptation Date: 3/22/2021
Adapted By: Alberta Health Services
Adaptation Reviewed By: Alberta Health Services
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