What Is HbA1c? – Definition, Charts, Target Levels

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When individuals experience symptoms of diabetes such as increased appetite, thirst, and frequent urination, accompanied by significant weight loss, they may undergo a test called glycated hemoglobin, or HbA1c, to determine whether they have diabetes. But what is HbA1c and how does it relate to diabetes? Let’s delve into it!

What’s HbA1c?

Glycated Hemoglobin, also known as HbA1c or simply A1C, is formed when the glucose in your blood sticks to your red blood cells and binds with the hemoglobin. Therefore, when there’s more glucose in your blood, there will be more glycated hemoglobin, or HbA1c.

When glucose binds with hemoglobin, the bond typically persists until the red blood cell reaches the end of its lifespan. Given that red blood cells live for about 120 days, testing HbA1c provides an indication of average blood sugar levels over the past 2 to 3 months. 

However, since HbA1c is the average blood sugar levels over the past 2 to 3 months, it cannot reveal the day-to-day variation in blood sugar levels. 

For example, two individuals can have the same value of HbA1c but the first might have a very high variation in blood sugar levels while those of the other individual remain stable.

What’s the Normal Range for an HbA1c Test?

What is the normal range for an HbA1c test? Different HbA1c readings indicate varying degrees of diabetic conditions:
HbA1c Range
Non-diabetic 4% – 5.6%
Pre-diabetes 5.7% – 6.4%
Diabetes ≥ 6.5%

Research has shown a negative correlation between HbA1c and mortality rates as well as complications associated with diabetes. For every 1% reduction in HbA1c, there’s a:

  • 21% decrease in the risk of mortality caused by diabetes,
  • 37% decrease in the risk of microvascular complications, and
  • 43% decrease in the risk of amputation in peripheral artery disease or related mortality.
Keeping your HbA1c value below 7% can greatly reduce the risk of diabetes-related complications.

The Relationship Between HbA1c and Blood Sugar

The conversion formula for estimated average glucose: (eAG) = 28.7 x HbA1c – 46.7 If your HbA1c is 7%, the eAG will be 28.7 x 7 – 46.7 = 154.2 (mg/dL). Below is a table with different HbA1c values and the corresponding eAGs:
HbA1c (%) eAG (mg/dL)
6 126
7 154
8 183
9 212
10 240
11 269
12 298

Why Do Blood Glucose and HbA1c Not Match?

When HbA1c Is Higher Than Expected:

When we say HbA1c is higher than expected, it means that the normal range of blood sugar levels for a person with diabetes is 80 – 140 mg/dL but the HbA1c value is higher than 8%, translating to an eAG value of 183 mg/dL.

The reason for this discrepancy may lie in inaccuracies in the blood sugar test methods, such as measuring blood sugar level at the same time but missing the postprandial high blood sugar period. It is recommended that individuals with diabetes discuss with their healthcare team to adjust their blood sugar measurement plan.

When HbA1c Is Lower Than Expected:

If blood sugar levels of an individual with diabetes usually fall within 120 – 180 mg/dL, but the HbA1c is only 6% (eAG: 126 mg/dL), the A1C is considered lower than expected.

There are several possible reasons behind this. Firstly, when measuring blood sugar levels, periods of low blood sugar may not be captured. Additionally, conditions such as hemoglobinopathies, changes in red blood cell turnover rates, impaired kidney function, or undergoing dialysis could also contribute to a lower-than-expected HbA1c value.

Is It Better for HbA1c to Be Lower?

Not necessarily. It’s more important to analyze changes in blood sugar levels over the past three months rather than simply focusing on HbA1c. For example, frequent episodes of hypoglycemia over a long period of time can increase the risk of dementia. Therefore, having a lower HbA1c is not always beneficial for blood sugar management.

Moreover, target blood sugar levels should be determined on a case-by-case basis. It is recommended to discuss your goals with your healthcare providers or refer to the table below for guidance on setting your HbA1c, pre-postprandial, and bedtime blood sugar levels.

HbA1c goals Target preprandial glucose levels (mg/dL) Target bedtime glucose levels (mg/dL) Suitable for
6.5% 80 - 120 90 - 120 Individuals without any complications, no risk of hypoglycemia
7.0% 80 - 130 90 - 130 Individuals with proper glycemic control, low risk of hypoglycemia
7.5% 90 - 130 90 - 150 < 18 years old with type 1 diabetes, on multiple daily injection insulin therapy
8.0% 90 - 150 100 - 180 Recurrent severe hypoglycemia, assitance needed for self-care
8.5% 100 - 180 110 - 200 Severe complications, assistance needed for self-care

How to Lower HbA1c?

Individuals with a high value of HbA1c can start by adjusting their lifestyle habits such as diet and exercise to help control A1C:

Diet

Developing healthy eating habits is essential to lowering your HbA1c. These habits include consuming fewer high-fat, high-sugar, and high-salt foods, and increasing the consumption of high-fiber foods such as vegetables. In addition, consider healthier cooking methods such as boiling, steaming, and stir-frying to decrease the amount of oil used.

Exercise

Research suggests that both aerobic and resistance exercise and improve insulin sensitivity and utilization, facilitating better glycemic control. It is generally recommended to engage in at least 150 minutes of moderate-intensity aerobic exercise per week. 

Medication

Certainly, following the doctor’s instructions regarding medication is crucial. Individuals with diabetes should monitor the effects of their medication on their blood sugar levels. If you feel that medication adjustments are necessary, it’s important to first consult your healthcare providers first without discontinuing your medication to avoid any unwanted effects.

Logging and Monitoring Data Daily to Help Stabilize Your HbA1c

After learning more about HbA1c, it’s important to know that logging your blood sugar levels everyday to know the changes in your blood sugar levels and adjusting lifestyle habits are key to controlling your HbA1c.

Health2Sync is an app with every feature you need to manage diabetes. You can not only log your blood sugar, HbA1c, but also have access to various graphs and charts to observe their long-term trends and stay informed about your health at all times.

Download Health2Sync Now!

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