HbA1c vs Fasting Blood Sugar: Which Test Is Better for Diabetes?

Summary

Diagnosis and screening of diabetes are conducted using two types of tests, HbA1c and Fasting Blood Sugar (FBS). While the two tests are similar, as they are both used to check blood glucose, their uses are not the same. The HbA1c test gives an average level of blood sugar for the past two to three months, hence useful in monitoring blood glucose control over the period. On the other hand, the fasting blood sugar test is used to measure blood glucose at a particular time after an overnight fast to measure current glucose levels and diagnose diabetes. The understanding of the difference between these tests will be beneficial in knowing when they are performed, their meaning, and why both tests can be used together for better evaluation of your glucose levels. It is important to be aware of early detection and monitoring of diabetes to prevent complications. If you are obese, have a family history of diabetes, or experience symptoms like excessive thirst and fatigue, seeking help from an internal medicine doctor would be beneficial.

Overview:

The HbA1c and fasting blood sugar tests are the most commonly recommended tests for diagnosis and management of diabetes. There are a lot of differences between these tests; that is why they cannot be used interchangeably. The HbA1c test shows you the average levels of blood sugar over a 2–3-month period. On the other hand, a fasting blood sugar test shows the levels of glucose in blood at one particular moment after an overnight fast.

With diabetes cases rising rapidly in India, choosing the right test can be confusing. Should you do an HbA1c test, a fasting blood sugar test, or both? The answer is that everything depends on your health condition, symptoms, and the needs of your doctor in the process of diagnosing or monitoring your diabetes.

If you are also confused about choosing the suitable test for you, this blog is for you. Here, you will find out how these tests differ from one another, what the purpose of each of them is, normal levels, advantages and disadvantages, and which test is more suitable for you.

Understand Blood Sugar Testing

It is essential to learn about both HbA1c and Fasting Blood Sugar (FBS) tests briefly before moving ahead with the comparison.

Glucose, or blood sugar, is the main source of energy for your body. However, continuous high blood sugar levels cause irreversible harm to your body organs such as the heart, kidneys, eyes, nerves, and blood vessels. A blood sugar test is a very significant one to diagnose diabetes early and prevent complications due to poor management of blood sugar levels.

"No single blood sugar test gives the full picture. It depends on what we want to know – your present glucose level or an average glucose level," according to Dr. Karabi Roy, Senior Pathologist at Miracles Healthcare, Gurgaon.

In general, healthcare practitioners recommend blood sugar tests for the following reasons:

  • Diagnosing diabetes

  • Identifying prediabetes

  • Checking glucose level control

  • Evaluating efficacy of diabetes treatment

  • Recognizing the risks of complications from diabetes

There are many blood sugar tests, among which two are commonly recommended. Those tests include the HbA1c test and Fasting Blood Sugar (FBS) test. Both are similar but have different significance. Knowing how these tests differ is the first step in knowing when your doctor may recommend one or both for accurate diagnosis and diabetes management.

Need an HbA1c or Fasting Blood Sugar Test? Book your test at Miracles Healthcare.

Call: 0124-4797600 | WhatsApp: +91 9820965000 

What Is the HbA1c Test

The HbA1c test, otherwise known as the Glycated Hemoglobin Test or Hemoglobin A1c Test, indicates the average levels of sugar present in your blood in the previous 2 to 3 months.

This is because glucose in the blood naturally binds to hemoglobin, which is a protein contained in red blood cells responsible for transporting oxygen. Because red blood cells have a lifespan of about 120 days, the HbA1c test provides information regarding the blood sugar levels over the past few weeks.

Unlike the usual blood sugar test, the HbA1c test shows the average level of your sugar levels in the previous months, rather than the current sugar levels.

                                   HbA1c Normal Range                                                        

         HbA1c Level

         Explanation

         Less than 5.7%

         Normal

        5.7% - 6.4%

         Prediabetes

        Above 6.5%

         Diabetes

In most patients with diabetes, a normal HbA1c level should be less than 7%. However, this may vary according to age, general well-being, and other underlying health problems.

What Is the Fasting Blood Sugar Test

The Fasting Blood Sugar (FBS) test measures your blood glucose level after fasting for at least 8 to 10  hours.

Since no food is consumed during the fasting period, the test shows how your body manages/ controls blood sugar without the influence of recent meals.

It is one of the oldest and most commonly performed tests for diagnosing diabetes.

Normal Fasting Blood Sugar Values

      Fasting Blood Sugar

      Interpretation     

      Less than 100 mg/dL

      Normal

     100–125 mg/dL

      Prediabetes

       126 mg/dL or higher (confirmed on repeat testing)

       Diabetes

To know more about the normal blood sugar level, check out our latest blog on "What should normal blood sugar levels be?"

HbA1c Test vs Fasting Blood Sugar Glucose Test

Factor                                                                         

HbA1c Test                                                                   

Fasting Blood Sugar Glucose Test                  

Measurement

Measures average blood sugar for 2 to 3 months

Measures blood sugar in a single instance

Requirement of Fasting

No

Yes

Shows Better Long-Term Results

Yes

No

Recent Intake of Food Does Not Affect the Results

Yes

No

Suitability

To diagnose and monitor diabetes

To diagnose and screen patients

Neither HbA1c nor fasting blood sugar is universally better. Together, they help doctors diagnose diabetes more accurately and monitor treatment effectively," says Dr. Karabi Roy

HbA1c Test Benefits

No Need to Fast: This is one of the greatest benefits offered by the test.

  1. Indicates Good Glucose Control: The test is an indicator of the overall sugar control of a person and not the fluctuations that are induced by factors such as food, stress, illness, and exercise.

  2. Predictor of Complications: Higher HbA1c levels indicate a higher risk for the following complications:

  • Kidney diseases

  • Diabetic retinopathy

  • Heart disease

  • Stroke

  • Nerve damage

Limitations of the HbA1c Test

Although highly useful, HbA1c is not suitable for everyone.

Its accuracy may be affected by

In such situations, your doctor may recommend fasting blood sugar or other glucose tests.

Benefits of the Fasting Blood Sugar Test

1. Convenient and Cheap: The fasting blood sugar test is very affordable and easily accessible.

2. Effective Tool for Diagnosis of the Problem: It is usually recommended as the first test to be conducted in case of the following signs:

  • Frequent urge to urinate

  • Intense thirst

  • Weight loss

  • Impaired vision

  • Weakness

3. Measures Instant Level of Blood Glucose: It determines the level of glucose in your body at the moment of testing.

Fasting Blood Sugar Test Limitations

In contrast to HbA1c, fasting blood sugar may show big variations depending on:

  • Your diet of the previous day

  • Stress factors

  • Any illness

  • The quality of your sleep

  • Physical activities

  • Some medications

This is why a doctor sometimes recommends this test two times or combines it with HbA1c for a better diagnosis.

Which Test is Best for Diagnosing Diabetes?

None of the diabetes blood tests can be said to be better than the other. Instead, they are complementary.

HbA1c is used when

  • There is a need to evaluate long-term blood sugar control

  • For monitoring diabetes

  • If fasting is hard

  • In health check-up screening for diabetes

FBS is used when

  • Need immediate information about blood sugar levels

  • When evaluating diabetes symptoms

  • When HbA1c is not reliable because of blood disorders

  • Need extra evidence for diagnosing diabetes.

Can You Have a Normal Fasting Blood Sugar but a High HbA1c?

Yes. This is more common than many people realize.

A normal result for the fasting blood sugar test does not necessarily mean that your blood sugar levels have been under control. Since the fasting blood sugar test measures the level of glucose in your blood at a single point in time, it cannot determine whether you have spikes in blood glucose during the day or after eating.

For instance, a patient can have:

  • Normal fasting blood sugar in the morning

  • High levels of blood sugar after meals

  • Frequent spikes of glucose in the daytime

In this case, the fasting blood sugar test will give a normal result while the HbA1c level will stay high since it indicates the average level of your blood sugar in the last 2-3 months.

"It's not uncommon for patients to have a normal fasting blood sugar but an elevated HbA1c. Looking at both results together provides a more complete understanding of a person's blood sugar control," says Dr. Karabi

What if fasting blood sugar is high but HbA1c is normal?

It is definitely possible under certain circumstances. If your HbA1C value is within the normal limits, then it means that the blood glucose has remained normal for the last 2-3 months. However, sometimes the fasting blood glucose may be high temporarily because of many factors influencing the blood glucose levels on that specific day.

This can occur due to the following:

  • Stress

  • Recent infection/illness

  • Poor sleep

  • Use of medication such as steroids

  • Changes in hormones

In such a situation, even though the HbA1c is normal, you might have a high fasting blood sugar level. The HbA1c test is indicative of blood sugar levels over a long period of time.

"A high fasting blood sugar level does not necessarily mean you have diabetes. It should be combined with HbA1c, other symptoms and, if necessary, further tests to determine the exact cause," says Dr. Roy

When there is an inconsistency between your HbA1c and fasting blood sugar levels, your doctor might recommend rechecking the fasting blood sugar levels or doing the Oral Glucose Tolerance Test (OGTT).

Who Should Get Diabetes Tested?

You should consider diabetes screening if you:

  • Are over 35 years of age

  • Are overweight or obese

  • Have a family history of diabetes

  • Have high blood pressure

  • Have high cholesterol

  • Have PCOS

  • Had gestational diabetes during pregnancy

  • Lead a sedentary lifestyle

  • Experience increased thirst, frequent urination, or unexplained weight loss

Regular screening helps detect diabetes before serious complications develop. 

Tips to Maintain Healthy Blood Sugar Levels

Regardless of whether you have a slightly high HbA1c or a slightly high fasting sugar, adopting a healthy lifestyle will make a difference.

1. Take a Healthy Diet

Eat:

  • Whole grains

  • Vegetables

  • Fruits in moderation

  • Proteins

  • Healthy fats

Avoid:

  • Sugary beverages

  • Refined carbs

  • Processed foods

  • Too many sweets

2. Exercise Frequently: You need to exercise frequently, that is, for about 150 minutes per week. You can walk briskly, cycle or swim.

3. Keep a Healthy Weight: Even a little weight loss, that is 5-10% weight reduction, is enough to enhance insulin sensitivity and glucose metabolism.

4. Get Enough Sleep: Not having enough sleep could affect your insulin level and elevate the amount of glucose.

5. Take Your Prescribed Medication: You need to take your prescribed medication for diabetes on time.

When to see a specialist?

If you suffer from:

If you are experiencing any or all of the mentioned issues, consult an internal medicine doctor near you. Timely diagnosis helps prevent complications in the future.

Take the Next Step Towards Better Diabetes Care

One of the most effective methods of avoiding diabetes-related complications is timely detection. Understanding whether an HbA1c test, a Fasting Blood Sugar test, or both tests should be performed will play a great role in the early detection and management of diabetes.

If you are prone to getting diabetes or need a thorough check-up of your blood sugar, visit an internal medicine doctor or schedule a blood sugar test near you at Miracles Healthcare, Gurgaon.

Comprehensive Diagnosis and Diabetes Management Under One Roof

Miracles Healthcare is the best multispeciality hospital in Gurgaon. We have been providing accurate comprehensive diagnostics, specialist consultations, and treatment under one roof for over two decades. Our team of specialists compares your current reports with previous test results for better diabetes monitoring.

  • Advanced Laboratory: Fully equipped with world-class diagnostic techniques by Roche, Bio-Rad, and bioMérieux for accurate results.

  • Diagnostic Range: Availability of 2,000+ diagnostic tests.

  • Quick Test Results: Normal test results in a span of 6 hours.

  • 24×7 Laboratory Facility: Full round-the-clock facility in case of emergency.

  • Sunday Reporting: Test reports of all the tests done on Sundays are available on the same day.

  • Easy Reports: Get your report via WhatsApp as well as access your report any time using the patient portal.

  • Expert Team: Skilled team of Pathologists and Microbiologists to perform quality tests.

  • Multispeciality Support: Access to Internal Medicine, Endocrinology, Cardiology, Nephrology, Ophthalmology, Nutritional experts, and other specialists to provide you with complete diabetes care.

  • Free Follow-Up Visit: Free follow-up consultation for eligible patients who come for prescribed tests to Miracles Healthcare (under hospital guidelines).

  • Multilocation Presence: With hospitals and clinics located in Sector 14, Sector 56, and Sector 82 of Gurgaon, the facilities of quality testing and specialist consultation can be easily obtained by patients.

Schedule your HbA1c and Fasting Blood Sugar Test near you at Miracles Healthcare today and get guidance from our specialists on time to diagnose and manage diabetes properly.

Written and Verified by:

Dr. Karabi Roy Exp: 14

MBBS, DCP

Frequently Asked Questions

Fasting blood sugar is more relevant than HbA1C in evaluating the present glucose levels.

Neither is universally more accurate; they measure different aspects of blood sugar and are often used together.

As per Dr Karabi, HbA1c at 9% or more is indicative of poor diabetes management and a higher risk of complications.

Eat a proper diet, exercise, take medicines regularly, and follow the doctor's instructions.

Yes, a blood sugar level of 230 mg/dL after meals is considered high.

Drinking water can not help in lowering HbA1c levels, although it is beneficial for overall health.

Diabetes usually affects the kidneys, eyes, heart, nerves, and blood vessels.

The level of HbA1c is considered unhealthy when it is 6.5% or more, whereas 7% is generally an indicator of poorly managed diabetes.