Blood Sugar Fluctuations: Insights from Continuous Glucose Monitoring

I have some questions regarding the use of continuous glucose monitoring devices?

Hello Doctor, I am 42 years old.
Last August, my health check revealed a fasting blood glucose level of 115 mg/dL and a hemoglobin A1c of 5.8%.
Since then, my fasting blood glucose has remained elevated, fluctuating between 108 and 114 mg/dL, with an A1c of 5.7% to 5.8%.
I purchased a continuous glucose monitor and used it for four days, which raised several questions I would like to discuss:
1.
I noticed that my average blood glucose levels throughout the day range from 100 to 150 mg/dL.
When fasting, my levels are around 80 to 120 mg/dL, and after eating, they rise to 150 to 160 mg/dL but return to below 140 mg/dL within two hours.
My pre-bedtime blood glucose is approximately 100 mg/dL.
Here are three recorded instances: A.
At 4:33 AM, the lowest was 75 mg/dL, then it rose to 106 mg/dL at 5:18 AM, dropped to 93 mg/dL at 5:48 AM, and gradually increased to 114 mg/dL by 7:30 AM.
B.
At 5:29 AM, the lowest was 74 mg/dL, gradually rising to 112 mg/dL by 7:30 AM.
C.
At 6:22 AM, the lowest was 86 mg/dL, rising to 108 mg/dL by 7:30 AM.
This may explain why my fasting blood glucose tests have consistently been over 100 mg/dL (prediabetes).
I have researched this symptom and found it resembles the Somogyi effect, which seems more common in Type 1 diabetes patients.
Since I was diagnosed with prediabetes at 41 years old, is it possible that I might be suspected of having Type 1 diabetes?
2.
I have been consistently weight training for over 10 years, and I noticed that during my workouts, my blood glucose can spike to around 220 mg/dL.
However, it typically returns to normal (around 120 mg/dL) about 30 to 40 minutes after finishing.
Is this normal? Can I continue with weight training?
3.
I observed that sometimes my post-meal blood glucose rises to 160 mg/dL during eating, but it usually drops below 140 mg/dL after about two hours.
Occasionally, when I eat plain steamed buns, my blood glucose can spike to 240 mg/dL, or if I overeat, it can rise to 220 mg/dL, but it often drops below 140 mg/dL within two hours, and sometimes even to 110 mg/dL.
This rapid increase and decrease— is this normal? Shouldn't blood glucose levels rise and fall more gradually for better management?
I apologize for the lengthy questions, and thank you for your assistance.

Ke Li Si, 40~49 year old female. Ask Date: 2024/05/26

Dr. Lin Wufu reply Internal Medicine

Hello, your question falls within the specialty of endocrinology, and the physician may need to ask you additional questions related to your diet and exercise in order to have a discussion.
Therefore, it is recommended that you visit the hospital to consult with the endocrinology outpatient department.

Reply Date: 2024/05/26

More Info

Understanding blood sugar fluctuations is crucial for managing prediabetes and preventing the onset of type 2 diabetes. Your experience with continuous glucose monitoring (CGM) provides valuable insights into how your body responds to various factors, including food intake, exercise, and possibly stress. Let's address your questions one by one.

1. Fluctuations and the Dawn Phenomenon: The pattern you described, where your blood sugar levels rise in the morning after a low overnight reading, is indeed reminiscent of the "dawn phenomenon." This phenomenon is characterized by an increase in blood sugar levels in the early morning due to hormonal changes, particularly the release of cortisol and other counter-regulatory hormones. While it is more commonly associated with type 1 diabetes, it can occur in individuals with type 2 diabetes or prediabetes as well. Given that you were diagnosed with prediabetes at 41, it is unlikely that you have type 1 diabetes, but it is essential to monitor these fluctuations closely. If your fasting blood sugar consistently exceeds 100 mg/dL, it indicates that your body is struggling to maintain normal glucose levels, which is a hallmark of insulin resistance.

2. Blood Sugar Response to Exercise: It is not uncommon for blood sugar levels to rise during intense exercise, particularly weight training. This increase can be attributed to the release of glucose from the liver and the breakdown of glycogen stores to provide energy for your muscles. The spike to 220 mg/dL during your workout is concerning but not unusual. The important aspect is that your blood sugar returns to normal levels (around 120 mg/dL) shortly after exercising. Continuing your weight training is beneficial for insulin sensitivity and overall health, but you should monitor your blood sugar closely before, during, and after workouts. If you notice significant spikes, consider adjusting your pre-workout nutrition or discussing your exercise regimen with a healthcare professional.

3. Postprandial Blood Sugar Levels: The rapid spikes in blood sugar after meals, especially after consuming refined carbohydrates like white bread, are indicative of how your body processes glucose. Ideally, blood sugar levels should rise gradually after eating and return to baseline levels within two hours. The fact that your blood sugar can spike to 240 mg/dL after meals and then drop back down to 140 mg/dL or lower suggests that your body is still capable of regulating blood sugar but may be experiencing insulin resistance. This pattern of rapid rise and fall is not ideal and can lead to long-term complications if not managed properly. It is advisable to focus on a balanced diet that includes complex carbohydrates, fiber, and protein to help stabilize blood sugar levels.

In summary, your CGM data provides a wealth of information about your glucose metabolism. While fluctuations are normal, the goal should be to minimize extreme highs and lows. Consider working with a healthcare provider or a registered dietitian who specializes in diabetes management to develop a personalized plan that includes dietary modifications, exercise strategies, and possibly medication if necessary. Regular monitoring and adjustments based on your CGM readings will empower you to take control of your health and reduce the risk of progressing to type 2 diabetes.

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