HbA1c test – DoctorOnHealth

Hemoglobin a1c (hba1c)

What is Hemoglobin a1c?

Hemoglobin A1C (HbA1c) is glucose coated hemoglobin A.

Hemoglobin a1c Test

Hba1c is a test that measures the amount of sugar attached with the hemoglobin A.

It is usually done in patients to diagnose diabetes (both type 1 and type 2 diabetes) and also in patients with diabetes to monitor the blood sugar levels. This test is known as glycated hemoglobin test, glycosylated hemoglobin, hemoglobin A1C or HbA1c test.

Hemoglobin carries oxygen in our blood. This test measures percentage of sugar coated hemoglobin in our blood. This test results gives the reflection of average blood sugar level for past 2-3 months as the RBC survives for about 3 months. So this is a highly useful test. When blood glucose level increases, blood glucose binds more to the hemoglobin. So, the HbA1C increase. 

Hemoglobin a1c Normal Range

HbA1C level below 5.7 percent is considered normal.

HbA1C level in between 5.7 percent to 6.4 percent is considered as prediabetes.

HbA1C level from 6.5 percent or higher on two separate tests indicate diabetes.

Hemoglobin a1c Levels

HbA1C test is interpreted as percentage. When the percentage of HbA1C is higher, it simply means higher average sugar level. 

As mentioned earlier, HbA1C level below 5.7% is considered normal.

In case of prediabetes that is in the range between 5.7 percent to 6.4 percent, the higher the level of your HbA1C percent, the more is the risk to develop a type 2 diabetes.

HbA1c percentage                           Estimated average glucose in mg/dL
Hba1c chart with corresponding blood sugar

Hemoglobin a1c (Hba1c) Test Purpose

The purpose of HbA1C test are the following 

  1. To diagnose prediabetes.
  2. To diagnose type 1 and type 2 diabetes
  3. To monitor the the health condition of the patient that is whether the patient is well managed with diabetes or not.
  4. To monitor the response of diabetes treatment.
  5. To determine if any modification of ongoing diabetes treatment is needed or not.
  6. To know whether the patient is at higher risk to develop diabetes complications.
  7. To determine the appropriate treatment for the patient.

Hemoglobin a1c (Hba1c) Test Importance

The importance of HbA1C test are the following

  1. To determine if any person has prediabetes or not. This will give an indication if any dietary modification is needed or not. People with prediabetes have higher chance to develop diabetes. So, appropriate treatment can be given to the patient on a timely manner. So in many cases, timely diagnosis of prediabetes helps to prevent development of diabetes through timely proper treatment.
  2. To know the average sugar levels for past 2-3 months. So response to the diabetic treatment can be easily understandable.
  3. To monitor type 1 and type 2 diabetes more effectively.
  4. To know the overall health condition of the patient as increased sugar level of blood causes poor immunity and diabetes associated complications.
  5. To predict the future risk of developing diabetes complications.
  6. Person with diabetes, if reduce their HbA1C by less than 1 percent, then they can cut their risk of dying within 5 years by 50 percent according to a Swedish research in the year 2012.

Why do I need an HbA1c test?

  1. Adults above 45 years older to screen for diabetes or prediabetes.
  2. Adults below 45 years older need this test when one has history of heart disease, kidney disease, high blood pressure, obese or overweight, nerve problems, eye problems ( more frequent inflammation of the eye, vision problems, etc.), pancreas problems, etc.
  3. Increased thirst, increased urination, weight loss, blurred vision, tingling or loss of sensation in the feet and hands, fatigue, delayed wound healing after a cut (if the cut is minor then also)- all these are common symptoms of diabetes. So, HbA1C test is needed to know the blood sugar level in the blood.

How often do you need the test?

HbA1c test, how often you need depends upon the following factors

  1. Type of diabetes
  2. Your health condition 
  3. Treatment plan
  4. Your response to treatment
  5. Your age
  6. Presence of other complications other than diabetes

HbA1c test can be done

  1. Once in a year if one has prediabetes 
  2. Twice in a year if one is not on insulin therapy and blood sugar level is consistently within the normal range or target range
  3. Four times in a year if one is under insulin or blood sugar level is not within normal range or target range.

Important to note that, HbA1C test  may need to be done more frequently if one is started with new medication of diabetes or any change of diabetes treatment plan if done.

So, type of diabetes ( type 1 or type 2) sugar level in the blood (whether control or uncontrolled), type of medication for diabetes one is using – all these determine how often you need to do the test.

Also, if you are diabetic or suspected to have diabetes, your doctor can tell you to do other additional blood sugar tests for accurate diagnosis of diabetes.

HemoglobinA1c (Hba1c) Test Procedure

It is a routine blood test like Fasting sugar test, PP sugar test, RBC blood test, WBC blood test, Platelet blood test, etc. No special precautions is needed. There is no restrictions of dietary intake or fluid intake. This test does not require a fasting. You can do the test any time in a day before or after eating.

Blood is taken from one vein ( preferably from vein of arm) and analysis of that blood sample is done on the laboratory. Also, small, pointed lancet can be used for finger pricking. Blood from finger prick can also be used for analysis.

Factors Interfering HbA1C Test Accuracy

The accuracy of HbA1C can be hampered by few factors such as

  1. Pregnancy (early or late)
  2. Insufficient red blood cells (anemia)
  3. Recent blood loss
  4. Heavy blood loss
  5. Hemoglobin variants ( for example, in thalassemia, sickle cell anemia, etc.)
  6. High cholesterol levels
  7. Kidney disease
  8. Liver disease
  9. Supplements such as vitamin C and vitamin E
  10. Certain medicines such as opioids,HIV medication. 

HbA1C test is not used to diagnose diabetes in gestatioational diabetes (diabetes only in pregnant women).

High Hemoglobin a1c

The higher HbA1C level than normal indicates poor control of blood sugar. Not only that, diabetes associated complications increase with higher HbA1C level. Higher HbA1C can be caused by  

  1. Anemia
  2. High dose aspirin
  3. Iron deficiency 
  4. Vitamin B12 and folate deficiency 

Hemoglobin a1c Low

Lower HbA1C can be caused by

  1. Pregnancy
  2. Blood transfusion recipients
  3. Chronic kidney disease treatment 
  4. Disorders affecting hemoglobin production such as sickle cell disease
  5. High alcohol intake

How to lower Hemoglobin a1c

In most of the cases, HbA1C level of less than 7 percent is a usual treatment target for adult diabetes patient. Based on individual, the target is determined, so the HbA1C target can be lower or higher based on clinical condition of that patient. Definitely, the main motto of diabetes treatment is to control the diabetes towards as normal as possible.

HbA1C less than 7 percent is associated with lower risk for developing diabetes associated complications. So, when HbA1C is more than the target level, then treatment modifications are needed to keep the HbA1C at target level. Diet, physical activity (exercise) and medication helps to control diabetes, so HbA1C becomes within normal range.

One with long untreated diabetes can have HbA1C level more than 8. So to lower HbA1c one needs to

  • Maintain dietary modifications such as lesser consumption of sugar, carbohydrates, higher consumption of fibers, green leafy vegetables, etc.
  • Physical activity as according age such as doing exercise regularly.
  • Adequate sleep to boost your immune system.
  • Stick to your medication as prescribed by your doctor
  • Regular follow up


HbA1C test measures the average blood sugar level in your blood for the past three months. But this test should not replace the regular blood sugar testing at home. Blood sugar changes throughout the day and night, sometime goes up, sometime goes down.

So, the daily variation of blood sugar level is not captured through this HbA1C test. So, one with steady blood sugar level and one with fluctuating blood sugar level (with high and low swings) can have same HbA1C level as this HbA1C test has nothing to do with daily variations of blood sugar, it reflects the average blood sugar level for previous 2- 3 months. So, always talk with your doctor and follow your doctors instructions regarding blood sugar control. Stay healthy and happy.


  1. Williams Textbook of Endocrinology E-Book
  2. Harrison’s Principles of Internal Medicine 20th edition
  3. Davidson’s Principles and Practice of Medicine 23rd edition
  4. Guyton and Hall Textbook of Medical Physiology
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