Is Abnormal Blood Sugar with Normal HbA1c a Sign of Diabetes?

Q: Is Abnormal Blood Sugar with Normal HbA1c a Sign of Diabetes?

Dear Mr. Huang： 1. According to the diagnostic criteria for diabetes set by the American Diabetes Association： a. A fasting plasma glucose level of ≥126 mg/dL after fasting for more than 8 hours; b. A 2-hour plasma glucose level of ≥200 mg/dL during an oral glu

Abnormal blood glucose levels with consistently normal glycated hemoglobin (HbA1c) may not necessarily indicate diabetes. It is important to consider other factors and conduct further testing to determine the underlying cause of the abnormal blood glucose levels?

Hello Doctor, for the past 4 to 5 years, my blood sugar levels during health check-ups have generally been normal, except for one instance where my fasting blood sugar was above 120.
I had an HbA1c test that showed 5.0, so no further treatment was initiated.
My weight has been around 90 kg.
Last August, my fasting blood sugar was about 140, and postprandial it was around 180, with an HbA1c of 5.1.
The doctor diagnosed me with diabetes and prescribed one Metformin pill.
Two months later, my fasting blood sugar was around 120, but postprandial it reached 220, while my HbA1c was approximately 5.2.
The doctor then added another medication.
After that, my blood sugar levels remained elevated, with fasting levels between 110 and 120, and postprandial levels between 160 and 180, while my HbA1c consistently stayed around 5.2.
This month, during my follow-up, my fasting blood sugar was 99, postprandial was 176, and my HbA1c was 4.9.
The doctor mentioned improvement and discontinued the second medication, prescribing only one Metformin pill.
During this period, my weight slightly decreased from 90 to 86 kg.

I would like to ask why my blood sugar levels have been consistently abnormal while my HbA1c has remained around 5.0.
Does this indicate diabetes? Additionally, is high blood sugar associated with a higher risk of inflammation or infection? Recently, when I visited dermatology, urology, and colorectal surgery, they all mentioned that I have diabetes and that my immune system is weak, making me more susceptible to infections and inflammation.
I asked my doctor about this, but he said the explanation is quite complex and might be difficult for me to understand, so I thought I would seek your advice.

Mr. Huang, 40~49 year old female. Ask Date: 2017/05/31

Dr. Xiao Yongxun reply Internal Medicine

Dear Mr.
Huang:
1.
According to the diagnostic criteria for diabetes set by the American Diabetes Association: a.
A fasting plasma glucose level of ≥126 mg/dL after fasting for more than 8 hours; b.
A 2-hour plasma glucose level of ≥200 mg/dL during an oral glucose tolerance test; c.
A hemoglobin A1c (HbA1c) level of ≥6.5% (this must be confirmed with a method that is certified by the National Glycohemoglobin Standardization Program (NGSP) and meets the Diabetes Control and Complications Trial (DCCT) standards).
The above conditions a, b, and c must be confirmed by two separate tests.
d.
If there are clinical symptoms of diabetes (such as polydipsia, polyuria, polyphagia, weight loss, etc.), a random plasma glucose level of ≥200 mg/dL is sufficient (this condition only requires one test).
2.
A study published in the Taiwan Family Medicine Journal (2012; 22: 141-149) reported that among 64,653 specimens, there were 27 cases with HbA1c values ≤4%.
The causes that may interfere with HbA1c measurement were categorized into four groups: (1) 8 cases of variant hemoglobin, all of which were Hb J; (2) 9 cases of hemolytic anemia, including 4 cases of G6PD deficiency and 4 cases of patients treated with ribavirin for hepatitis C; (3) 7 cases of upper gastrointestinal bleeding, including 5 cases of liver cirrhosis; (4) 3 cases of anemia with undetermined causes.
Compared to cases without variant hemoglobin, those with variant hemoglobin had lower HbA1c values (p=0.008) and higher hemoglobin levels (p=0.002).
3.
Therefore, your physician is correct.
In your case, it is important to consider variant hemoglobin, hemolytic anemia, gastrointestinal bleeding, and other possible causes.
However, diabetes testing should not rely solely on HbA1c; pre-meal and post-meal blood glucose levels, weight, waist circumference, body mass index, and related clinical symptoms or conditions are all important indicators.
4.
Current research indicates that the main risk factors for developing type 2 diabetes include obesity, a family history of diabetes, lack of physical activity, a history of cardiovascular disease, a history of gestational diabetes or giving birth to a baby weighing over 4 kg, polycystic ovary syndrome, acanthosis nigricans, dyslipidemia, and hypertension.
Your current condition should still be manageable; however, if you have more risk factors, please take early action to prevent worsening and becoming harder to control in the future.
5.
Type 2 diabetes does not occur suddenly; it develops gradually due to factors such as obesity, poor dietary habits, lack of exercise, and unhealthy lifestyle choices.
Essentially, anyone with a family history of diabetes should be advised to control their diet and exercise early on to manage their weight; this can help avoid the nightmare of diabetes.
In other words, the progression of diabetes from non-existence to existence, and from mild to severe, is a gradual process.
6.
Regarding practical dietary and exercise improvement plans, I personally recommend that you: chew your food slowly during meals, avoid overeating (aim for about 80% fullness), and limit high-calorie, high-fat, and high-sugar foods or beverages.
Reduce intake of high-cholesterol and trans fats (often found in creamers, butter, ghee, instant coffee, milk tea, etc.) and high fructose corn syrup (commonly found in commercial beverages, desserts, sodas, pastries, etc.).
These types of foods may be harder for the body to metabolize, may contain empty calories that do not provide satiety, and can easily lead to elevated blood sugar levels.
On the other hand, it is important to develop a regular exercise routine, such as playing sports, jogging, swimming, or cycling; in fact, taking a good walk for 30-60 minutes after each meal can have excellent effects.
In terms of lifestyle, avoid excessive stress and ensure adequate sleep; this will help reduce the secretion of related hyperglycemic hormones and increase the secretion of leptin, aiding in weight control.

Reply Date: 2017/05/31

More Info

Abnormal blood sugar levels with a normal HbA1c can indeed be indicative of diabetes, particularly in the context of fluctuating blood glucose levels. To understand this better, let’s break down the relationship between blood sugar levels, HbA1c, and diabetes.

Understanding Blood Sugar and HbA1c
1. Blood Sugar Levels: Blood glucose levels can vary significantly throughout the day based on food intake, physical activity, and other factors. Normal fasting blood glucose levels are typically below 100 mg/dL, while levels between 100 mg/dL and 125 mg/dL indicate prediabetes, and levels of 126 mg/dL or higher on two separate tests confirm diabetes.

2. HbA1c: The HbA1c test measures the average blood glucose levels over the past two to three months. An HbA1c of 5.7% to 6.4% indicates prediabetes, while an HbA1c of 6.5% or higher is diagnostic for diabetes. Your readings of 5.0% to 5.2% suggest that, on average, your blood sugar levels have been within a normal range.

The Discrepancy Between Blood Sugar and HbA1c
In your case, despite having abnormal blood sugar levels (e.g., fasting blood sugar of 140 mg/dL and postprandial levels reaching 220 mg/dL), your HbA1c remains relatively low. This discrepancy can occur for several reasons:
- Glycation Variability: Individuals with certain conditions, such as hemoglobinopathies or anemia, may have altered HbA1c results. However, you mentioned having Mediterranean anemia, which can affect the accuracy of HbA1c readings.

- Recent Changes: If your blood sugar levels have recently spiked but have not been sustained over the long term, your HbA1c may not yet reflect these changes. HbA1c is a lagging indicator, meaning it takes time for changes in blood sugar to be reflected in the HbA1c levels.

- Diet and Lifestyle: If you have made dietary changes or increased physical activity, these factors can lead to fluctuations in blood sugar levels while maintaining a stable HbA1c.

Diabetes Diagnosis and Management
Given your fluctuating blood sugar levels and the context of your HbA1c readings, it is essential to consider the following:
- Diagnosis: Your healthcare provider may consider you to have diabetes based on your elevated blood sugar levels, despite a normal HbA1c. This is particularly true if you have symptoms or if your blood sugar levels are consistently high.

- Medication: The use of medications like metformin (伏糖) is common in managing blood sugar levels. It appears that your doctor is adjusting your medication based on your blood sugar readings, which is appropriate.

- Monitoring: Regular monitoring of both blood glucose and HbA1c is crucial. It helps in understanding your overall glycemic control and adjusting treatment as necessary.

Infections and Immune Response
Regarding your concerns about infections and inflammation, elevated blood sugar levels can indeed impair immune function. High glucose levels can lead to:
- Increased Susceptibility to Infections: High blood sugar can weaken the immune response, making it easier for infections to take hold.

- Delayed Healing: Elevated glucose levels can also slow down the healing process, which is why you might be experiencing more frequent infections.

Conclusion
In summary, while your HbA1c levels suggest good average blood sugar control, the abnormal blood sugar readings indicate that you may still be at risk for diabetes or may already have it. It is crucial to continue working closely with your healthcare provider to monitor your blood sugar levels, adjust medications as needed, and address any potential complications, including infections. Regular follow-ups and lifestyle modifications, such as diet and exercise, will also play a significant role in managing your condition effectively.

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