Elevated Fasting Blood Sugar with Normal HbA1c Levels

Fasting blood glucose is elevated, but glycated hemoglobin (HbA1c) levels are normal?

I have undergone five health check-ups over the past two years, and each time my fasting blood glucose has been around 110 mg/dL.
However, my hemoglobin A1c has consistently been around 5.3%.
During these two years, I have been diligent about exercising, and my weight has decreased from 79 kg to 69 kg.
I am 174 cm tall, my BMI is normal, and I have gained significant muscle mass.
Despite these efforts, my blood glucose levels have not shown significant changes.
In my health check-up at the end of November, my fasting blood glucose was 110 mg/dL and my hemoglobin A1c was 5.2%.
Could you please explain the reasons for this? How can I improve my situation?

Mr. Chen, 50~59 year old female. Ask Date: 2018/12/14

Dr. Hou Angting reply Family Medicine

Currently, the diagnosis of diabetes is assessed based on both fasting blood glucose and glycated hemoglobin levels.
According to your situation, a high fasting blood glucose level with a normal glycated hemoglobin level can rule out diabetes.
However, it is important to maintain a healthy diet and engage in regular exercise, and to follow up with a family medicine specialist.
If you have any related questions, you can discuss them with your physician during your follow-up appointments.

Reply Date: 2018/12/14

More Info

Elevated fasting blood sugar levels, particularly when consistently around 110 mg/dL, can be concerning, especially when accompanied by normal HbA1c levels, which in your case have been around 5.2 to 5.3%. This situation is often referred to as "impaired fasting glucose" or "prediabetes," and it can be perplexing for individuals who maintain a healthy lifestyle, including regular exercise and weight management.

Firstly, it’s important to understand the relationship between fasting blood sugar and HbA1c. Fasting blood sugar measures the glucose level in your blood after an overnight fast, while HbA1c reflects your average blood glucose levels over the past two to three months. In your case, the fasting blood sugar levels are slightly elevated, indicating that your body may not be processing glucose as effectively as it should, yet your HbA1c levels remain within the normal range, suggesting that your overall blood sugar control is still good.

Several factors could contribute to this discrepancy:
1. Physiological Variability: Blood sugar levels can fluctuate due to various factors, including stress, sleep quality, hydration status, and even the timing of your last meal. If you are experiencing stress or poor sleep, this could lead to transient increases in blood sugar levels.

2. Insulin Sensitivity: Regular exercise and weight loss generally improve insulin sensitivity, but individual responses can vary. Some people may still experience elevated fasting blood sugar levels despite a healthy lifestyle due to genetic factors or underlying metabolic conditions.

3. Dawn Phenomenon: This is a natural increase in blood sugar that occurs in the early morning due to hormonal changes in the body. Cortisol, glucagon, and epinephrine levels rise in the morning, which can lead to increased glucose production by the liver, resulting in elevated fasting blood sugar levels.

4. Dietary Factors: Even with a healthy diet, certain foods can impact blood sugar levels. For example, high carbohydrate meals or snacks before bedtime can influence morning fasting blood sugar levels. It may be beneficial to monitor your carbohydrate intake and meal timing.

5. Underlying Conditions: Conditions such as metabolic syndrome or prediabetes can cause elevated fasting blood sugar levels while maintaining normal HbA1c levels. It’s essential to rule out any underlying health issues that may be contributing to your blood sugar levels.

To improve your fasting blood sugar levels, consider the following strategies:
- Monitor Your Diet: Keep a food diary to track your meals and identify any patterns that may correlate with elevated blood sugar levels. Focus on a balanced diet rich in whole grains, lean proteins, healthy fats, and plenty of fruits and vegetables.

- Exercise Regularly: Continue your exercise regimen, but consider incorporating a mix of aerobic and resistance training. High-intensity interval training (HIIT) has also been shown to improve insulin sensitivity.

- Manage Stress: Engage in stress-reducing activities such as yoga, meditation, or deep breathing exercises. Chronic stress can negatively impact blood sugar levels.

- Sleep Hygiene: Ensure you are getting adequate and quality sleep, as poor sleep can affect insulin sensitivity and blood sugar control.

- Regular Monitoring: Keep track of your blood sugar levels at different times of the day, including postprandial (after meals) readings, to gain a better understanding of how your body responds to different foods and activities.

- Consult a Healthcare Professional: Given your persistent elevated fasting blood sugar levels, it may be beneficial to consult with a healthcare provider or a registered dietitian. They can provide personalized advice and may recommend further testing to rule out any underlying conditions.

In summary, while your HbA1c levels indicate good overall blood sugar control, the consistently elevated fasting blood sugar levels warrant further investigation and lifestyle adjustments. By focusing on diet, exercise, stress management, and regular monitoring, you can work towards improving your fasting blood sugar levels and overall metabolic health.

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