The A1C test is a common blood test used to diagnose type 1 and type 2 diabetes and to monitor how well diabetes is being managed. The A1C test has many other names, including glycated hemoglobin, glycosylated hemoglobin, hemoglobin A1C and HbA1c.
Results of the A1C test reflects the average blood sugar level for the past two to three months. Specifically, the A1C test measures what percentage of hemoglobin (a protein in red blood cells that carries oxygen) is coated with sugar (sugar). The higher the A1C level, the poorer the sugar control, and the higher the risk of diabetes complications.
The A1C test is carried out for the following reasons;
- Identify prediabetes
- Diagnose type 1 and type 2 diabetes: to confirm diabetes diagnosis, results of two blood tests administered on different days ¾ either two Q&C tests or the Q&C test plus another diabetes blood test will be checked.
- Monitor diabetes treatment plan: the results of the initial A1C test(s) also help establish baseline A1C test plus another diabetes blood test. The A1C test is then repeated regularly to monitor the diabetes treatment plan. Since it measures average blood glucose levels for the past two to three months, it can thus show how well the diabetes treatment plan is working to lower the blood sugar over time.
A normal A1C level is 5.6 percent or below (97mg/dL), according to the National Institute of Diabetes and Digestive and Kidney Diseases. A level of 5.7 to 6.4 percent (97-126mg/dL) indicates prediabetes. People with diabetes have an A1C level of 6.5 percent or above (126mg/dL).
Setting goals for A1C levels.
The target A1C level for people with diabetes is usually less than 7% (<152mg/dL). The higher the hemoglobin A1C, the higher the risk of having complications related to diabetes.
A combination of diet, exercise, and medication can bring down A1C levels. People with diabetes should have an A1C test every 3 months to make sure their blood sugar is within the target range.
Can the A1C test be used during pregnancy?
The A1C test can be used in early pregnancy to detect if a woman with risk factors had undiagnosed diabetes before she got pregnant. This is because the A1C test shows the average blood glucose over 3 months. As such when the teat is done early in pregnancy, the results will include values reflecting the pre-pregnancy period.
Can other blood glucose tests be used to diagnose type 2 diabetes and prediabetes?
Other tests used for type 2 diabetes and prediabetes diagnosis include the oral glucose tolerance test and fasting blood glucose test. These two tests are done after fasting for 8hours. If diabetes is suspected, the health care provider can carry out the random blood glucose test to the A1C test to confirm the presence of diabetes
Can the A1C test result in a different diagnosis than blood glucose tests?
In some cases, the results of a blood glucose test might be different from that of the A1C test. The blood glucose test may detect diabetes when the A1C does not. Likewise, the A1C can detect diabetes while the blood glucose test does not. As a result of these variations, repeat tests are carried out before diagnosis.
Differences in test results can be in the early stages of diabetes when blood glucose has not escalated enough to show up in every test. In this case, the patients are closely followed up and tests repeated in several months
What causes variations in diabetes blood test results?
Diabetes blood test results can vary from day to day and from test to test, due to the following reasons:
- Blood glucose levels fluctuate.
Natural changes in the body can lead to variations in blood glucose levels. A typical example is when your blood glucose levels spike after a high glycemic index carbohydrate meal and drops when you exercise or eat low carbohydrate diets. Other factors that can cause these fluctuations to include stress, and sickness. These short term changes in blood glucose levels are more visible in the oral glucose tolerance test and the fasting blood glucose test than the A1C test
- A1C tests can be affected by changes in red blood cells or hemoglobin
Conditions that change the life span of red blood cells, such as recent blood loss, sickle cell disease, erythropoietin treatment, hemodialysis, or transfusion, can change A1C levels.
For example, iron deficiency anemia can affect the A1C test by giving falsely high results. Kidney failure and liver disease are other causes of faulty A1C results
- Small changes in temperature, equipment, or sample handling
Even when the same blood sample is repeatedly measured in the same lab, the results may vary because of small changes in temperature, equipment, or sample handling. These factors tend to affect glucose measurements; fasting blood glucose and the oral glucose tolerance test more than the A1C test.
How precise is the A1C test?
A1C test results can be slightly higher or lower than the initial measurement after they are repeated. For example, an A1C reported as 6.8 percent on one test could be reported in a range from 6.4 to 7.2 percent on a repeat test from the same blood sample. Before this range was larger, however stricter quality control measures have been put in place to ensure more accurate results.
How is the A1C test used after the diagnosis of diabetes?
Diabetes experts recommend that patients take the A1C test every year. The A1C test results are used to plan treatment targets, modify diabetes therapy where necessary, and monitor the disease management. If treatment targets are not being attained, diabetes professionals may require that you run the test more often.
What should be my target A1C goal?
A1C test targets vary in different individuals. This depends on their general health and diabetes history. Research has shown that some people with diabetes can reduce the risk of diabetes-associated complications by maintaining A1C levels below 7%.
Proper management of blood glucose levels can reduce the risk of complications and provide long term health benefits. It is important to note that an A1C level that is safe for someone might be unsafe for another. For example, keeping an A1C level below 7 percent may not be safe if it leads to problems with hypoglycemia.
Less strict blood glucose control, or an A1C between 7 and 8 percent or even higher in some circumstances may be appropriate in people with the following conditions:
- Long-term complications diabetes complications such as glaucoma, kidney disease, neuropathy, and cardiovascular disease.
- Persistent high glucose levels with an inability to drop.
- Terminal illness with limited life expectancy.
- An extreme drop in glucose levels, also known as hypoglycemia.
Will the A1C test show short-term changes in blood glucose levels?
The A1C test result can show a huge sway in blood glucose levels over a month, but will not show a sudden temporary rise or falls in blood glucose levels. Although A1C results show long term blood glucose levels, the glucose levels within the past 30 days have more impact on A1C values than the previous months.
The A1C test detects the average amount of blood sugar in over 2 to 4 months by measuring your glycated hemoglobin. The test does not show acute temporary increases or decreases in blood glucose levels. The presence of abnormal hemoglobin such as hemoglobin S in your blood may lead to a decrease in hemoglobin A. This eventually affects the amount of glucose that can bind to your hemoglobin and may limit the usefulness of the A1C test in monitoring your diabetes.
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- Enzo Bonora and Jaakko Tuomilehto (2011) The Pros and Cons of Diagnosing Diabetes With A1C. Diabetes care 34 Suppl 2(Suppl 2): S184-90 DOI: 10.2337/dc11-s216