the Gap Between Fasting and Post-Meal Blood Sugar Levels

Q: the Gap Between Fasting and Post-Meal Blood Sugar Levels

Dear Ms. Anna： 1. According to the American Diabetes Association's diagnostic criteria for diabetes： a. Fasting plasma glucose level ≥126 mg/dL after fasting for more than 8 hours, b. Plasma glucose level ≥200 mg/dL during a 2-hour oral glucose tolerance test,

The difference between fasting blood glucose and postprandial blood glucose after breakfast?

Hello Doctor, during my first pregnancy, I had gestational diabetes, and I did not follow up or manage it after giving birth.
During the early stages of my second pregnancy, I underwent testing and was diagnosed with diabetes.
Throughout my second pregnancy, I controlled my blood sugar with insulin.
After giving birth, my doctor observed my blood sugar levels and suggested that I could start with dietary management.
However, in the past couple of months, due to a busy schedule and frequent trips, I haven't measured my blood sugar for a long time.
This morning, I reminded myself to check, and my fasting blood sugar was 134 mg/dL, and two hours after eating, it was 176 mg/dL.
Previously, my fasting blood sugar was around 110 mg/dL (the doctor mentioned that this is characteristic of diabetes and it cannot drop below 100 mg/dL).
Does this fasting level indicate that I need to start insulin again? Is it too high? However, the postprandial difference of 176 mg/dL is only 42 mg/dL, and as far as I know, a difference of less than 60 mg/dL is considered normal.
Since my follow-up appointment is not yet due, I wanted to consult with you first.
Thank you!

Anna, 30~39 year old female. Ask Date: 2016/05/30

Dr. Xiao Yongxun reply Internal Medicine

Dear Ms.
Anna:
1.
According to the American Diabetes Association's diagnostic criteria for diabetes: a.
Fasting plasma glucose level ≥126 mg/dL after fasting for more than 8 hours, b.
Plasma glucose level ≥200 mg/dL during a 2-hour oral glucose tolerance test, c.
HbA1c (glycated hemoglobin) ≥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 criteria a, b, and c must be confirmed on two separate occasions.
d.
Clinical symptoms of diabetes (such as polyuria, polydipsia, polyphagia, and weight loss) with any plasma glucose level ≥200 mg/dL (this can be confirmed with just one test).
2.
Generally, postprandial blood glucose levels gradually rise, peak at around two hours after eating, and then gradually decline.
If high-sugar or high-calorie foods are consumed and there is sufficient insulin secretion in the body, blood glucose levels may spike rapidly, potentially peaking within one hour after a meal before gradually decreasing.
The term "two hours postprandial" refers to two hours after the start of eating.
In medical practice, for convenience in treatment or discussion, postprandial blood glucose levels are typically referenced at the two-hour mark.
In healthy individuals, postprandial plasma glucose levels are below 140 mg/dL, while those with impaired glucose tolerance have postprandial plasma glucose levels between 140 and 180 mg/dL.
If postprandial plasma glucose levels exceed 180 mg/dL, the risk of diabetes should be considered.
3.
During pregnancy, if diabetes occurs, it is generally managed with insulin injections to avoid the potential side effects of oral medications on the fetus.
Regarding your current situation, it does not necessarily mean that insulin injections are required.
Your physician's recommendation to first manage your condition through diet and exercise is indeed a very appropriate decision.
Insulin or oral medications can quickly bring blood glucose levels to an ideal state; however, the risk of hypoglycemia must be considered, so please discuss this in detail with your physician.
4.
In fact, dietary control, regular exercise, timely medication adherence, and lifestyle improvements remain the cornerstone of diabetes management.

Reply Date: 2016/05/30

More Info

Understanding the gap between fasting and post-meal blood sugar levels is crucial, especially for individuals with a history of gestational diabetes or those who have transitioned into type 2 diabetes. Your situation highlights the importance of monitoring blood sugar levels and understanding the implications of those readings.

Firstly, let's clarify what constitutes normal blood sugar levels. According to the American Diabetes Association (ADA), normal fasting blood glucose levels should be below 100 mg/dL. A fasting blood glucose level between 100 and 125 mg/dL indicates impaired fasting glucose, which is a precursor to diabetes. A reading of 126 mg/dL or higher on two separate tests confirms a diagnosis of diabetes. Post-meal (postprandial) blood sugar levels should ideally be below 140 mg/dL two hours after eating. A reading of 176 mg/dL, as you mentioned, is above this threshold and indicates that your body is struggling to manage glucose effectively after meals.

In your case, a fasting blood sugar level of 134 mg/dL is concerning, especially given your history of gestational diabetes and the fact that you were previously on insulin therapy. This level suggests that your body may not be adequately regulating blood sugar levels, and it could indicate a progression toward type 2 diabetes. The fact that your fasting levels have been around 110 mg/dL previously, which is still above normal, further emphasizes the need for careful monitoring and potential intervention.

The gap between your fasting and post-meal blood sugar levels (42 mg/dL) is indeed within the acceptable range, as a difference of 60 mg/dL or less is generally considered normal. However, the absolute values of your blood sugar readings are more critical in determining your overall glucose control. The fasting level of 134 mg/dL is particularly concerning, as it is significantly above the normal range and suggests that your body is not effectively managing glucose levels overnight or during fasting periods.

Given your history and current readings, it is essential to consult with your healthcare provider. They may recommend a few strategies:
1. Dietary Adjustments: Focus on a balanced diet rich in whole grains, lean proteins, healthy fats, and plenty of fruits and vegetables. Monitoring carbohydrate intake is crucial, as carbohydrates have the most significant impact on blood sugar levels.

2. Regular Monitoring: Keep a close eye on your blood sugar levels, both fasting and post-meal. This will help you and your healthcare provider understand your patterns and make informed decisions about your management plan.

3. Physical Activity: Regular exercise can help improve insulin sensitivity and lower blood sugar levels. Aim for at least 150 minutes of moderate-intensity aerobic activity each week, along with strength training exercises.

4. Medication Review: If your blood sugar levels remain elevated, your healthcare provider may consider reintroducing insulin or other medications to help manage your blood sugar levels effectively.

5. Follow-Up Appointments: Regular follow-ups with your healthcare provider are essential to monitor your condition and adjust your management plan as needed.

In summary, your current fasting blood sugar level of 134 mg/dL is a sign that you may need to reassess your diabetes management plan. While the gap between fasting and post-meal levels is within a normal range, the absolute values indicate that your blood sugar control may not be optimal. It is crucial to discuss these findings with your healthcare provider to determine the best course of action, which may include dietary changes, increased physical activity, and possibly medication adjustments.

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