Discrepancies Between Blood Sugar Tests and Home Monitoring

The blood glucose test results from the lab are normal, but self-monitoring shows elevated levels?

Hello, Doctor.
Thank you for taking the time to read my lengthy description.
About four weeks ago, I visited the hospital's endocrinology department due to concerns about my blood sugar levels.
The doctor ordered blood tests to assess the situation, and all results came back normal: fasting blood sugar was 90 mg/dL, OGTT (Oral Glucose Tolerance Test) showed 97 mg/dL before drinking the glucose solution and 111 mg/dL two hours later, and my HbA1c was 5.5%.
Additionally, my two-hour postprandial blood sugar was 74 mg/dL, which was taken on a different day.
The doctor indicated that my blood sugar levels were fine.

However, after returning home, I measured my postprandial blood sugar and found it exceeding 140 mg/dL, which I found concerning.
I continued to randomly test my postprandial blood sugar, and the results showed that my fasting and breakfast blood sugar levels were normal, but my lunch and dinner levels were more unstable.
It seems that when I consume particularly oily foods (like fried noodles or mixed rice), my blood sugar levels rise significantly, ranging from 144 to 174 mg/dL two hours after eating.
On the other hand, if I eat lighter meals, my levels remain below 140 mg/dL.

The educational materials state that "normal individuals typically reach their peak postprandial blood sugar one hour after eating, usually not exceeding 140 mg/dL." Since I have had several instances of exceeding 140 mg/dL two hours after meals, does this indicate that something is wrong? Is there a possibility of prediabetes? However, the hospital's blood tests showed no issues.
Should I return to the hospital for further evaluation, or should I continue to monitor my condition for a while? I am a bit confused about how to proceed.
Thank you for your guidance.

Banxia A-Tang, 30~39 year old female. Ask Date: 2019/09/04

Dr. Lin Jianliang reply Internal Medicine

Your condition may indicate impaired glucose tolerance, which may not yet meet the criteria for a diabetes diagnosis.
It is recommended to manage your diet and exercise for a period of time, and then follow up at the hospital.
If you experience any symptoms, seek immediate follow-up.

Reply Date: 2019/09/04

More Info

Understanding discrepancies between blood sugar tests and home monitoring can be quite complex, especially when considering the various factors that can influence blood glucose levels. Your situation highlights a common concern among patients who are monitoring their blood sugar levels at home while also undergoing formal testing in a clinical setting.

Firstly, it’s important to understand the differences between the types of blood glucose measurements. In a clinical setting, blood glucose levels are typically measured using venous blood samples, which are processed in a laboratory. This method generally provides a more accurate representation of blood glucose levels compared to home monitoring devices, which often measure capillary blood from a finger prick. The results from these two methods can differ due to several factors, including the timing of the test, the method of measurement, and even the physiological state of the individual at the time of testing.

In your case, the laboratory results indicated normal blood glucose levels: fasting glucose at 90 mg/dL, an oral glucose tolerance test (OGTT) result of 111 mg/dL two hours post-ingestion, and a hemoglobin A1c (HbA1c) of 5.5%. These results suggest that your glucose metabolism is functioning well at the time of testing. However, your home monitoring has shown postprandial (after meal) blood sugar levels exceeding 140 mg/dL, particularly after consuming high-fat or high-carbohydrate meals.

The American Diabetes Association (ADA) defines normal postprandial blood glucose levels as less than 180 mg/dL two hours after eating. However, for optimal health, many healthcare providers recommend that postprandial levels should ideally remain below 140 mg/dL. Your readings of 144-174 mg/dL after certain meals could indicate that your body is having difficulty managing blood sugar spikes, particularly with meals that are higher in fat or carbohydrates.

This discrepancy raises a few important considerations:
1. Dietary Impact: The composition of your meals can significantly affect your blood sugar levels. High-fat meals can slow gastric emptying, which may lead to delayed spikes in blood sugar. It’s essential to monitor how different foods affect your glucose levels and adjust your diet accordingly.

2. Insulin Sensitivity: It’s possible that your body is becoming less sensitive to insulin, especially after consuming certain types of foods. This can lead to higher postprandial glucose levels. Regular physical activity and maintaining a healthy weight can improve insulin sensitivity.

3. Monitoring and Follow-Up: Given your concerns and the discrepancies between your home monitoring and clinical results, it would be prudent to continue monitoring your blood sugar levels. If you consistently see postprandial levels above 140 mg/dL, especially after meals that are not excessively high in carbohydrates or fats, it would be wise to consult with your healthcare provider. They may recommend further testing or a referral to an endocrinologist for a more comprehensive evaluation.

4. Potential for Prediabetes: While your lab results are currently normal, the elevated postprandial readings could suggest a risk for developing prediabetes or type 2 diabetes in the future. It’s essential to address any lifestyle factors that may contribute to this risk, such as diet, exercise, and weight management.

In conclusion, while your laboratory results indicate that you are currently within normal ranges, your home monitoring suggests that there may be some issues with postprandial glucose control. It’s advisable to keep a detailed log of your food intake and corresponding blood sugar levels, and to discuss these findings with your healthcare provider. They can help you interpret these results in the context of your overall health and may suggest dietary modifications, lifestyle changes, or further testing to ensure that you maintain optimal blood sugar control.

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