What is Glycated Hemoglobin(A1c) Test?

Glycated hemoglobin

The glycated hemoglobin is a test is a routine method for testing the quantity of sugar in the blood during the preceding few months. It’s used to diagnose diabetes or assess how effectively a person with the disease has managed their blood sugar levels. Different forms of hemoglobin (a protein found in red blood cells) may impact findings in some persons.

What is Glycated Hemoglobin?

Blood flowing through the body consist of Red Blood cells which carry a protein named Hemoglobin. The main function of Hemoglobin is to carry oxygen. This oxygen-carrying hemoglobin when combined with glucose then becomes glycated hemoglobin.

The average life span of Red blood cells is 120 days. So measurement of HbA1c gives an average picture of blood sugar levels over a period past few months. This test could be very helpful in monitoring the control over diabetic and prediabetic patients.


Diabetes mellitus, often known as diabetes, is a metabolic disorder marked by high blood sugar levels. Insulin transports sugar from the bloodstream into the cells, where it is stored or used for energy. Your body either doesn’t generate adequate insulin or can’t use the insulin it does make it efficiently if you have diabetes.

If left unaddressed, diabetes-related high blood glucose levels can affect your nerves, eyes, kidneys, and other organs.


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Types of Diabetes

Diabetes is divided into several types:

Type 1Diabetes:

It is an autoimmune condition. Pancreas where insulin is produced is attacked by the immunity mechanism and destroys cells. The reason for this is unknown. About 10 % of the diabetic population is Diabetes Type 1.

Type 2 Diabetes

When the body develops resistance to insulin, sugar builds up in the bloodstream, resulting in type 2 diabetes.


Prediabetes is a state in which your blood sugar level is greater than usual but not high enough to be confirmed with type 2 diabetes.

Gestational Diabetes

High blood sugar during pregnancy is known as gestational diabetes. This kind of diabetes is caused by the production of insulin-blocking substances by the placenta.

Symptoms of Diabetes

The common symptoms of diabetes include:

  • Increase in feeling of hunger
  • Increase in feeling of thirst
  • Loss of weight
  • Polyuria
  • Delusional Vision
  • Weakness and fatigue
  • Unhealing wounds for long period
Glycated hemoglobin
Fig1: Symptoms of Diabetes

Why Glycated Hemoglobin?

The HbA1c test is based on the plasma glucose level attached to RBC and the average life of RBC is 4 months. This test is the best marker for monitoring diabetic control and diagnosing a pre-diabetic condition.

The amount of glucose that combines with the hemoglobin present in the RBC is directly proportional to the plasma sugar level in our body at that period of time.

For people who have diabetes this test help clinicians to monitor how much good control you have in your diabetes over the last few months. For people whose A1c control is not satisfactory, they are advised for this test every 3-6 months.

For the people whose HbA1c value falls under the prediabetic range, they are advised to perform the test every 1-2 years.

Risk Factors for A1c

Risk factors
Fig2: Causes of diabetes

The Centre for Disease and Control has suggested that adults over the age of 45 get tested for screening of diabetes and pre-diabetes. If less than 45 years of age there’s are some risk factors that strongly suggest screening for diabetic or pre-diabetic conditions.

  • High Blood Pressure
  • Sedative lifestyle
  • Obese/ Overweight
  • History Of heart disease
  • Any symptoms of diabetes
    • Increased Thirst
    • Increased Urination
    • Blurred Vision
    • Fatigue
    • Loss of weight

How is Hba1c measured?

The A1c molecule has its own electrical charge which is distinguishable from the charge of other components of hemoglobin. Besides this, the size of the A1c molecule is also different from other molecules of hemoglobin.

High-Performance Liquid Chromatography is an advanced technique that can easily differentiate between the charge and size of hemoglobin “A”1c molecule with other hemoglobin A molecules.HPLC method uses different liquid reagents mixes them on blood sample passes it through high pressure and analyzes the value of glucose bound hemoglobin molecule.

Glycosylated hemoglobin is not affected by a short-term variation in blood like meals, exercise, etc that is why a fasting sample is not needed.

Glycated hemoglobin
Fig3: How is glycated hemoglobin measured

Why choose HbA1c over Blood Glucose?

Blood Glucose level only shows the amount of glucose present in your blood at the time of the test done. This is only an indicator for the current glucose level rather than concentration over a certain period.

Blood glucose levels can be tested simply by drawing blood either from the veins of the arm or from the finger. Depending upon the diet intake test could be done as fasting, postprandial or random

For HbA1c no extra preparation is needed. No fasting is needed.HbA1c level is the indicator of the overall concentration of glucose on average of 3 months. This test can be done at any time of the day. This test helps to monitor the diabetic control and onset of the prediabetic stage.

Normal levels of HbA1c

For people who do not have diabetes, the normal range of glycosylated hemoglobin is 4%-5.6%, 5.7% to 6.4% is the indicator of risk for diabetes in the future, and levels above 6.4 indicate diabetes.

Normal of Hba1c
Fig4: Normal range of glycated hemoglobin

Defining Target for HbA1c in diabetic cases

Diabetic subjects should try to maintain the A1c value lower than 7.0%. The value of HbA1c is directly proportional to the risk of complications related to diabetes. The treatment plan by the clinician depends upon the value of A1c.

The analogy of Blood Glucose and HbA1c readings

The figure below shows how HbA1c(%), is compared to the average blood glucose level in mmol.

hba1c and blood glucose level
Fig5: Comparision of glycated hemoglobin with blood glucose

Complications of Higher HbA1c

Different studies have demonstrated that a higher level of A1C could increase the risk of microvascular complications. Some studies among diabetic subjects in the UK proved that a 1%increase in A1c(11mmol/l) will increase the risk of microvascular complications by 25%.

Microvascular complications include:

  • Retinopathy
  • Neuropathy
  • Diabetic Nephropathy ​
  • Some studies have also shown that people suffering from diabetes decreasing Hba1c by 1% is 19% less likely to suffer from cataracts, 16% less likely to suffer from heart failure, and 43% less likely to suffer from vascular diseases.

Limitations Of HbA1c

Though the HbA1c test is often valid there are some cons regarding this test. This test is not always reliable for every group of subjects.

  • Pregnant woman: In pregnancy, there may be the presence of an uncommon form of hemoglobin also known as hemoglobin variant and, therefore result in inaccurate results
  • Anemia: People with anemia may have less hemoglobin due to which HbA1c can not be taken as a good investigation. Instead, a fructosamine test is preferred.
  • Recent Severe Bleeding
  • Recent Blood Transfusions
  • Chronic Kidney disease
  • Chronic Liver disease
  • Hemoglobin Variants like sickle cell hemoglobin(HbS)

Preventive Measures for lowering HbA1c

Even a small decrease in HbA1c could show very significant changes. But diet, exercise, and lifestyle changes are the simplest measures to keep your A1c in control.

Physical Activity:150-300 minutes of exercise is recommended for a healthy lifestyle per week. In the case of insulin administration, a plan with a doctor should be made for proper results.

Monitoring Glucose: A target should be set up to maintain good control over glucose levels and regular monitoring is needed.

Weight Management: A goal should be set up in maintaining the weight.

Tracking Progress: Tracing progress is for self-encouragement and self-motivation.

Dietary measurements: Eating regularly every 3-5 hours, eating less carbohydrate-rich foods, focusing on foods rich in fiber like fruits, whole grains, vegetables especially non-processed foods could help lower A1c levels.

De-stress: Try to stay free from stress. Because many studies have shown that stress is somehow related to an increased level of blood glucose and glycosylated hemoglobin value.

 General FAQs

Do A1c need a fasting sample?

Since HbA1c is the average measurement of glucose from the part of red blood cells it does not need a fasting sample

What are the factors that can affect A1c?

Increased A1cs can be seen in iron deficiency, vitamin B12 deficiency, decreased erythropoiesis, hyperbilirubinemia, alcohol dependency, large doses of aspirin, chronic opiate use.
Variability in A1c can be seen in hemoglobinopathies and decreased A1cs can be seen in hypertriglyceridemia

How frequently should A1c be done?

For patients with good control over sugar levels two times a year is sufficient whereas for poorly controlled patients it may increase up to four times year

Can we rely on HbA1c?

Since A1c is average of three months of blood sugar level it can be taken as a wonderful biomarker and indicator of insulin resistance and can be used as reliable test to diagnose diabetic and prediabetic condition.

What is the wonder fruit that helps in diabetes?

MiraBurst is a fruit that could be beneficial for diabetics and pre- diabetics. It is said that MiraBurst help body to increase the sensitivity towards their insulin and control blood glucose levels.


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