Hemoglobin is a protein found on the surface of red blood cells that primarily functions to carry oxygen and deliver it to various organs in the body. When glucose enters the bloodstream, it binds to hemoglobin, forming glycated hemoglobin.
Since the lifespan of red blood cells is typically around 120 days, glycated hemoglobin serves as an indicator of blood glucose levels over the past 2 to 3 months, with a recommended testing frequency of once every 3 months. However, it’s important to note that glycated hemoglobin is not the sole indicator and should be evaluated alongside fasting blood sugar and postprandial blood sugar.
Generally, the normal range for glycated hemoglobin is 4.0% to 5.6%. Levels between 5.7% and 6.4% are considered high, while ≥6.5% is indicative of diabetes.
Glycated hemoglobin can be converted to an average blood glucose value over the past 3 months using the following formula:
Average Blood Glucose (mg/dL) = (Glycated Hemoglobin – 5) × 35 + 100
For example, if the glycated hemoglobin value is 6%, the approximate average blood glucose over the past 3 months would be: (6 – 5) × 35 + 100 = 135 mg/dL.
| Glycated Hemoglobin (%) | Average Blood Glucose (mmol/L) |
| 5 | 5.4 |
| 5.5 | 6.2 |
| 6 | 7 |
| 6.5 | 7.8 |
| 7 | 8.6 |
| 7.5 | 9.4 |
| 8 | 10.2 |
| 8.5 | 10.9 |
| 9 | 11.7 |
| 9.5 | 12.5 |
| 10 | 13.3 |
If glycated hemoglobin is low (<5.5%), even if the value is still within the normal range, there is a higher chance of experiencing impaired bodily functions compared to the general population.
Elevated glycated hemoglobin indicates a risk of developing diabetes, but with early control, it is possible to avoid a diabetes diagnosis.
Glycated hemoglobin is the combination of hemoglobin and glucose, so any abnormalities in hemoglobin concentration can potentially affect glycated hemoglobin levels.
Individuals with iron-deficiency anemia have difficulty producing new red blood cells, resulting in a higher proportion of older red blood cells that have a longer time of glucose binding, leading to increased glycated hemoglobin levels.
Reduce the intake of foods that cause a sudden spike in blood sugar, including high-sugar, high-calorie, or high-carbohydrate foods. Increase consumption of vegetables and consider implementing a low-carbohydrate diet if necessary.
It is recommended to engage in approximately 150 minutes of moderate-intensity exercise per week and incorporate weight training to enhance insulin sensitivity.
Research suggests that losing 5 to 10% of body weight can reduce the risk of developing diabetes by 58%.
Since the average lifespan of red blood cells is around 120 days and glycated hemoglobin is not easily removed once formed, the concentration of glycated hemoglobin reflects the blood glucose level over the past 2 to 3 months. In other words, it is recommended to test glycated hemoglobin every 3 months.
If the glycated hemoglobin value is high, it could be an early sign of declining bodily functions associated with aging. If this condition occurs in older individuals, it is advisable to seek medical attention early to prevent worsening of the condition.
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