Postprandial (Post-Meal) Glucose
| Author: Judy Kohn, RN, BSN, CDE |
| Last Updated: Thursday, November 15, 2007 |
Q: "I have type 2 diabetes. In class much emphasis was put on the blood sugar 2 hours after eating. Why is this so crucial?"
A: You ask a very important question - and one which is still being debated. Since you mentioned diabetes class, I suspect you might be fairly new to diabetes; don't let this answer overwhelm you, but rather, please print it out and take it to your next diabetes session.
Defined: Blood glucose 2 hours after a meal is often called the post-meal glucose, or in medical terms, the postprandial glucose, or PPG for short. The American Diabetes Association (ADA) defines the 2-hour PPG as: a measurement of glucose 2 hours after the start of the meal.
Importance of the 2-hour PPG:
- Risk of complications: Recent studies have shown that people with high 2-hour PPG levels have a higher incidence of cardiovascular disease. Studies have also shown that people with high 2-hour PPG levels have an increased incidence of microvascular complications (meaning eye, nerve, and kidney problems).
- Many people with type 2 diabetes lose what is called their first phase insulin release: Insulin is released in two phases, the first phase being within 10 minutes of eating; when this phase is lost, it means that the glucose goes abnormally high after the meal because there isn't adequate insulin to handle the food.
- A1C can sometimes be misleading: Many experts emphasize using the A1C to evaluate overall control (A1C is the blood test done every 3-6 months that reflects the average glucose level over the past 2-3 months). But this test can be misleading for several reasons: you could have blood glucose levels between 60 and 300 mg/dl and yet have an average glucose of 130, and an A1C of 7%. Yet this would not necessarily mean you were in good control.
- For years, people only thought they should test before meals; many were stunned to discover that their pre-meal glucose levels were within target range, yet their 2-hour PPG levels were extremely elevated.
- The 2-hour PPG test can help you analyze the effect of your food, activity and medication to help you determine if you need to modify your meal plan, increase your activity, and/or change your diabetes medication.
Discussions about the 2-hour PPG:
- Recent developments: Although many studies are indicating that both the pre-meal and post-meal blood glucose levels are important, it was only recently that we had the means to not only measure frequent glucose levels but also target the post-meal glucose levels with various new oral agents and/or newer insulins.
- Does A1C correlate closer with fasting or 2-hour PPG? There are even conflicting studies debating whether the A1C is more closely correlated with the fasting glucose or with the 2-hour PPG. There are studies supporting both sides. Regardless of the outcome, most researchers feel the evidence is overwhelming that achieving near-normal pre and post-meal glucose levels is essential to achieving overall good diabetes control.
- Ongoing Studies: Studies are ongoing to determine if targeting specifically the 2-hour PPG will prevent complications. The ADA Clinical Practice Recommendations state that if the pre-meal glucose values are within target but the A1C is not at target, then consider monitoring PPG 1-2 hours after the start of the meal and aim treatment to reduce the average PPG value to less than 180 mg/dL. However the ADA noted that the effect of these approaches on the microvascular or macrovascular complications has not been studied.
- Opinions vary on the glucose goals: The American Association of Clinical Endocrinologists (AACE) has taken the stand advocating strict glucose control both pre-meal (under 110 mg/dL) and post-meal (under 140 mg/dL). The International Diabetes Federation (IDF) recommends a pre-meal glucose under 100 mg/dL, and a post-meal glucose under 140 mg/dL. Many experts agree that they don't want to wait all the years it will take to prove that post prandial testing is important.
Conclusions:
- Keep in mind that it is not enough to just test after meals: for example, if you were at target goal before the meal, but too high after the meal, you could conclude that either you ate too much at that meal, or that you need to add or adjust your medication. But if you are too high both before and after the meal, then the fault lies not necessarily in that meal, but rather in the meal, or medication, or activity that occurred prior to that pre-meal test.
- For a review of how monitoring can help, as well as suggested testing times, please review the related questions listed below.
- Be sure to discuss all this with your healthcare team.
Related Questions
Why test if not on diabetes medication?
Q:
"I have Type 2 and am getting high numbers when I test. A type 1 can take
insulin if high. What can I do to lower my number? Almost seems senseless to
test if I cannot take action to remedy the results..."
Glucose Goals
Q:
"What is a good blood glucose reading?"
Important Notice: The responses provided by the team of Diabetes Educators are based on their personal experiences and expertise as practicing diabetes healthcare professionals, and are not to be considered diabetes management advice from Abbott Laboratories. Remember that information provided by the team of Diabetes Educators is for general background purposes and is not intended as a substitute for medical diagnosis or treatment by a trained professional. You should always consult your physician about any healthcare questions you may have, especially before trying a new medication, diet, fitness program, or approach to healthcare issues.
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