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What is Hemoglobin A1C (HbA1C) in Blood Test? What is High and Low Hemoglobin A1C (HbA1C) Level? Causes & Treatment?

Updated: Jun 17, 2024

  • Hemoglobin A1C (HbA1C) in the blood test is a test that shows the average blood sugar (glucose) level in the blood over the past two to three months.

  • Hemoglobin is a protein found in blood. It gives the blood its red color and allows oxygen to be carried throughout the body. Glucose is the building block of carbohydrates and meets the body's energy needs. If there is a problem in the body regarding the use and storage of glucose in the blood, excess glucose sticks to hemoglobin and remains in the blood for an average of 2-3 months. As blood sugar levels increase, the number of hemoglobin bound to glucose also increases. The HbA1C test measures the level of these glucose-bound hemoglobin. In this way, glucose levels accumulated in the blood can be measured.

  • Its difference from the sugar test is that it gives an idea about the average glucose value of 2-3 months.

  • Being hungry or full does not affect the test result.

  • The HbA1C test is used to diagnose type 2 diabetes or prediabetes. It is also used to monitor the effectiveness of treatment.

  • The other names are A1C, glycohemoglobin, glycated hemoglobin, glycosylated hemoglobin.

Hemoglobin A1C (HbA1C) in the blood test is a test that shows the average blood sugar (glucose) level in the blood over the past two to three months. Hemoglobin is a protein found in blood. It gives the blood its red color and allows oxygen to be carried throughout the body. Glucose is the building block of carbohydrates and meets the body's energy needs. If there is a problem in the body regarding the use and storage of glucose in the blood, excess glucose sticks to hemoglobin and remains in the blood for an average of 2-3 months. As blood sugar levels increase, the number of hemoglobin bound to glucose also increases. The HbA1C test measures the level of these glucose-bound hemoglobin. In this way, glucose levels accumulated in the blood can be measured. Its difference from the sugar test is that it gives an idea about the average glucose value of 2-3 months. Being hungry or full does not affect the test result. The HbA1C test is used to diagnose type 2 diabetes or prediabetes. It is also used to monitor the effectiveness of treatment. The other names are A1C, glycohemoglobin, glycated hemoglobin, glycosylated hemoglobin. In a blood test, the normal HbA1C value should be between 4% and 5.7%. Some medications and some diseases can affect the results of an HbA1C test. Anemia, kidney failure, and liver problems can directly affect blood sugar and cause different test results. The person's health history and medications used before the test are important for evaluation. In a blood test, high Hemoglobin A1C (HbA1C) is defined as over 5.7%. If the HbA1C value is high, it means that the sugar in the blood cannot be used or the excess sugar cannot be stored in the muscles and liver, meaning it remains in circulation. If the test result is higher than normal, your doctor may ask you to have another A1C test or a different type of diabetes test (usually a fasting blood sugar test or oral glucose tolerance test (OGTT)). High sugar in the blood is called hyperglycemia.
What is Hemoglobin A1C (HbA1C) in Blood Test? What is High and Low Hemoglobin A1C (HbA1C) Level? Causes & Treatment?

What is A Normal Hemoglobin A1C (HbA1C) Level in Blood Test ?

In a blood test, the normal HbA1C value should be between 4% and 5.7%. Some medications and some diseases can affect the results of an HbA1C test. Anemia, kidney failure, and liver problems can directly affect blood sugar and cause different test results. The person's health history and medications used before the test are important for evaluation.


What is High Hemoglobin A1C (HbA1C) Level in Blood Test?

  • In a blood test, high Hemoglobin A1C (HbA1C) is defined as over 5.7%. High HbA1C is evaluated in two different reference ranges.

    • 5.7% to 6.4% (117-137 mg/dl) prediabetes

    • 6.5% (140 mg/dl) and above diabetes

    • %7 - 154 mg/dL

    • %8 - 183 mg/dL

    • %9 - 212 mg/dL

    • %10 - 240 mg/dL

    • %11 - 269 mg/dL

    • %12 - 298 mg/dL

  • If the HbA1C value is high, it means that the sugar in the blood cannot be used or the excess sugar cannot be stored in the muscles and liver, meaning it remains in circulation.

  • If the test result is higher than normal, your doctor may ask you to have another A1C test or a different type of diabetes test (usually a fasting blood sugar test or oral glucose tolerance test (OGTT)).

  • High sugar in the blood is called hyperglycemia.


What Causes High Hemoglobin A1C (HbA1C) Level in Blood Test?

The cause of high HbA1C value is prediabetes or diabetes. However, some factors related to hemoglobin may cause the result to be high. These may include anemia, some medications, and some tumors.


High Hemoglobin A1C (HbA1C) Symptoms

Possible symptoms that may occur with high HbA1C include:

  • Feeling very thirsty

  • Urinating a lot

  • Losing weight

  • Feeling very hungry

  • Blurred vision

  • Numb or tingling hands or feet

  • Fatigue

  • Dry skin

  • Sores that heal slowly

  • Having more infections than usual


How to Treat High Hemoglobin A1C (HbA1C) Level?

The most effective method to reduce high Hba1C levels is to regulate blood sugar. For this, the treatment plan, nutrition plan, medication and insulin injection scheme must be determined by the doctor. Hyperglycemia and hypoglycemia are prevented by adjusting insulin doses in insulin-dependent diabetic patients. In the nutrition plan, it is necessary to stay away from carbohydrate and sugary foods that increase blood sugar. Instead, emphasis should be placed on vegetables and fiber-rich foods. It is very important to drink plenty of water and exercise.


What is Low Hemoglobin A1C (HbA1C) Level in Blood Test?

Low HbA1c is when the blood sugar level is below the lower reference value. This is a value below 4%. Low HbA1C is rare and may indicate an underlying medical condition.


What Causes Low Hemoglobin A1C (HbA1C) Level in Blood Test?

Low HbA1C may be caused by hypoglycemia. However, HbA1C may also be low for reasons unrelated to diabetes. These reasons are:

  • Overuse of diabetes medications

  • Liver disease

  • Alcohol use disorder

  • Bleeding

  • Kidney failure

  • Pregnancy


Low Hemoglobin A1C (HbA1C) Symptoms

Possible symptoms that may occur with low HbA1C include:

  • Sweating

  • Chills

  • Hunger

  • Irritability

  • Speech disorder

  • Blurred vision

  • Fainting


How to Treat Low Hemoglobin A1C (HbA1C) Level?

In case of hypoglycemia, efforts are made to increase blood sugar levels to normal levels in the treatment of low HbA1C.

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