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What is the Hemoglobin A1C Test?

The Hemoglobin A1C test is a vital blood test that measures your average blood sugar levels over the past three months. It's a key tool in managing diabetes, providing a snapshot of long-term glucose control. With clear images to guide you, understanding this test becomes simpler. How might your A1C levels influence your health journey? Let's find out together.
Helga George
Helga George

The hemoglobin A1c (A1c) test is a measure of blood sugar levels that is more reliable than the standard finger prick test performed at home, using a blood sugar meter. Hemoglobin is the major protein in red blood cells and carries oxygen throughout the body. If sugar levels are high in the blood, they will bind to hemoglobin. This forms glycated hemoglobin, which is detected by a hemoglobin A1c laboratory test. This reading provides a blood sugar measurement to help diagnose diabetes mellitus, or to help patients determine how well they are keeping their blood sugar under control.

Even when diabetic patients persistently monitor blood glucose levels at home using a blood sugar meter, there is quite a bit of variation in blood sugar levels. These levels often fluctuate throughout the day. It is difficult to get an accurate estimate of the overall blood sugar levels using this technique. The hemoglobin A1c test provides a reliable measure of blood sugar levels over the past three months, which is the approximate lifespan of a red blood cell.

Red blood cells containing hemoglobin.
Red blood cells containing hemoglobin.

Once sugar binds to the hemoglobin, it stays bound. Since it measures the amount of glycated hemoglobin in the red blood cells, the hemoglobin A1c test provides an estimate of blood sugar levels over the preceding months. A reading of between 4 to 6% is considered normal. Levels of 6.5 to 7% indicate a diagnosis of diabetes.

One might expect that low levels from a hemoglobin A1c test would be considered healthy for a diabetic, but this may not be the case. Diabetics struggle with high blood sugars, but low levels of blood sugars — hypoglycemia — can often be a problem as well. This is particularly true for Type 1 diabetics, who must inject insulin, or Type II diabetics on certain medications. Extreme levels of hypoglycemia can cause loss of consciousness and death. It is possible that low hemoglobin A1c test results indicate a mix of incidents of high blood glucose and hypoglycemia.

Individuals with diabetes can struggle with both high and low blood sugar levels.
Individuals with diabetes can struggle with both high and low blood sugar levels.

It is considered desirable for diabetics to have hemoglobin A1c levels below 6.5%. This correlates with a lowered degree of complications from diabetes, such as blindness, kidney problems, cardiovascular problems, gangrene, and loss of feeling in the feet. A patient should consult with his doctor to determine an ideal target range that will minimize high blood sugar levels, without causing hypoglycemia.

Individuals with low hemoglobin levels may be unable to donate blood.
Individuals with low hemoglobin levels may be unable to donate blood.

There are certain individuals for whom the hemoglobin A1c test is not recommended. People with certain types of anemia, such as hemolytic and sickle cell, degrade their blood cells. In other words, the red blood cells do not live a full three months. Also, people with Vitamin 12 or folic acid deficiency have blood cells that live much longer than normal. Individuals with these conditions are advised not to utilize this method of measuring their long-term blood sugar levels.

A person's blood sugar levels fluctuate throughout the day.
A person's blood sugar levels fluctuate throughout the day.

There is an alternate test to measure fructosamine levels, which is sometimes used instead of the hemoglobin A1c test, for patients who require it, such as those with hemolytic anemia. Unfortunately, it only measures blood sugar levels from the past two to three weeks. This test measures the reaction of glucose in the blood, with blood proteins, such as albumin. One such test is known as the glycated albumin test.

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Discussion Comments

anon356004

I recently had blood work done. my doctor sent me a letter saying my A1c level was OK, but limit sweets. What does that mean and should I be concerned? I hardly ever eat sweets.

anon327104

Is it possible that hypoglycemia increases the hemoglobin level?

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    • Red blood cells containing hemoglobin.
      By: Steve Young
      Red blood cells containing hemoglobin.
    • Individuals with diabetes can struggle with both high and low blood sugar levels.
      By: Rob Byron
      Individuals with diabetes can struggle with both high and low blood sugar levels.
    • Individuals with low hemoglobin levels may be unable to donate blood.
      By: Gina Sanders
      Individuals with low hemoglobin levels may be unable to donate blood.
    • A person's blood sugar levels fluctuate throughout the day.
      By: Monkey Business
      A person's blood sugar levels fluctuate throughout the day.
    • The hemoglobin A1C laboratory test is the most accurate way to measure blood glucose.
      By: spflaum
      The hemoglobin A1C laboratory test is the most accurate way to measure blood glucose.
    • A patient should consult with their doctor to determine their ideal blood sugar levels.
      By: JackF
      A patient should consult with their doctor to determine their ideal blood sugar levels.