Hemoglobin A1C (HbA1c) test is performed for doctors to check for prediabetes and diabetes or assess the effectiveness of diabetes treatment. It measures the average amount of sugar in your blood over the past 3 months. A result between 5.7 and 6.4% suggests pre-diabetes and any value above 6.5% indicates diabetes.
But what exactly is hemoglobin? How does an HbA1c test work and what are the target values for different individuals? We’ll explore everything you need to know about HbA1c in this blog post.
Table of Content
What Is Hemoglobin?
Hemoglobin is a type of protein in the red blood cells. Its main function is to carry oxygen around your body and deliver it to different tissues.
What Is an HbA1c Test?
When the sugar, or glucose, in your blood binds with the hemoglobin, it will become glycated hemoglobin. When there’s more glucose in your blood, there will be more glycated hemoglobin.
The HbA1c, or A1C, test then measures the percentage of red blood cells with glycated hemoglobin. When the bond is formed, it typically persists until the red blood cells reach the end of the 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 fluctuation of 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?
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.
How to Calculate eAG from HbA1c?
Estimated average glucose (eAG) is an estimated number of your blood sugar based on your HbA1c.
The conversion formula for eAG from HbA1c is as follows:
If your HbA1c is 7%, the eAG will be 28.7 x 7 – 46.7 = 154.2 (mg/dL).
Below is a chart 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 if this happens.
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.
Target HbA1c and Blood Sugar Levels for Different Groups
Below is a chart showing the HbA1c goals for different groups and the corresponding target preprandial and bedtime blood sugar levels.
| HbA1c goals | Target preprandial blood sugar levels (mg/dL) | Target bedtime blood sugar 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.
Keeping Track of Blood Sugar Everyday Helps Stabilize Your HbA1c
After learning more about HbA1c, it’s important to know that logging your blood sugar levels everyday 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.
