Fasting vs. Postprandial Blood Sugar Levels: A Patient's Concern

Q: Fasting vs. Postprandial Blood Sugar Levels: A Patient's Concern

Hello： I had milk tea around 3-4 PM. <br>I tested my blood sugar at 6 PM, which is considered postprandial blood sugar (2 hours after eating), not fasting blood sugar.

Is it considered preprandial blood glucose or postprandial blood glucose?

I have a history of hypertension and take my medication every morning before meals.
My blood pressure is currently well-controlled.
I am 158 cm tall, weigh 55 kg, and am 44 years old.
On the evening of August 10th at 6 PM, I had a follow-up appointment to pick up my medication, and the doctor recommended routine blood tests.
The nurse performed a fasting blood glucose test and asked if I had eaten dinner.
I replied that I had not.
The result showed a blood glucose level of 110 mg/dL, but the nurse did not comment further and allowed me to take my medication home.
The report has not yet been released.

I am a bit worried and looked up related information online.
The normal fasting blood glucose range is 70-99 mg/dL, and 110 mg/dL seems to indicate prediabetes.
However, I had milk tea around 3-4 PM, which does not meet the eight-hour fasting standard.
Given that the test was done at 6 PM, does this count as postprandial blood glucose (2 hours after eating)? I am really confused and concerned, and I hope to clarify these issues before the report is available.
Thank you!

Anne, 40~49 year old female. Ask Date: 2023/08/13

Dr. Lin Jianliang reply Internal Medicine

Hello: I had milk tea around 3-4 PM.
I tested my blood sugar at 6 PM, which is considered postprandial blood sugar (2 hours after eating), not fasting blood sugar.

Reply Date: 2023/08/13

More Info

Understanding fasting and postprandial blood sugar levels is crucial for managing your health, especially given your concerns about potential prediabetes. Let's break down your situation and clarify some key points regarding blood sugar testing.

Fasting Blood Sugar Levels
Fasting blood sugar is typically measured after an overnight fast of at least 8 hours. The normal range for fasting blood sugar is generally considered to be between 70 and 99 mg/dL. A fasting blood sugar level of 100 to 125 mg/dL indicates prediabetes, while a level of 126 mg/dL or higher suggests diabetes.
In your case, a fasting blood sugar level of 110 mg/dL does fall into the prediabetes range. However, it's important to consider the context of the test. If you had not eaten for at least 8 hours before the test, then this reading is significant. If you had consumed anything, especially something high in sugar or carbohydrates, it could affect the accuracy of the fasting measurement.

Postprandial Blood Sugar Levels
Postprandial blood sugar levels are measured after eating. Typically, blood sugar is tested 1 to 2 hours after a meal. Normal postprandial blood sugar levels should be less than 140 mg/dL. If you had a milk tea in the afternoon, it could certainly affect your blood sugar levels, especially if it contained sugar. However, since your test was conducted in the evening and you had not eaten since your last meal, the reading should reflect your fasting state, assuming you adhered to the fasting guidelines.

Timing and Accuracy of Blood Sugar Tests
Your concern about the timing of your blood sugar test is valid. If you consumed milk tea in the afternoon, it would not directly impact your fasting blood sugar reading taken later that evening, provided you had not eaten anything else since your last meal. However, if you had a significant amount of sugar in that milk tea, it could potentially affect your overall glucose metabolism, leading to fluctuations in your blood sugar levels.

Recommendations
1. Follow-Up Testing: Since your fasting blood sugar is at the borderline of prediabetes, it would be wise to follow up with your healthcare provider. They may recommend further testing, such as an HbA1c test, which provides an average blood sugar level over the past 2-3 months.

2. Monitor Your Diet: Pay attention to your carbohydrate intake, especially refined sugars and processed foods. A balanced diet rich in whole grains, fruits, vegetables, and lean proteins can help manage blood sugar levels.

3. Regular Exercise: Incorporating regular physical activity can help improve insulin sensitivity and lower blood sugar levels. Aim for at least 150 minutes of moderate aerobic activity each week.

4. Stay Informed: Keep track of your blood pressure and blood sugar levels. Regular monitoring can help you and your healthcare provider make informed decisions about your health.

5. Consult Your Doctor: Discuss your concerns with your healthcare provider, especially regarding your blood pressure medication and any potential interactions with your blood sugar levels.

In summary, while your fasting blood sugar of 110 mg/dL is concerning, it is essential to consider the context of the test and follow up with your healthcare provider for further evaluation and guidance. Maintaining a healthy lifestyle and being proactive about your health can significantly impact your overall well-being.

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