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Glucose Testing: After Meals?

Should diabetics test their blood sugars after eating, too? The debate continues.
WebMD Feature

Every diabetic is familiar with fasting blood glucose tests. You don't eat for at least eight hours, you check your blood sugar, and by that, you establish what your baseline glucose is.

This was at least the traditional idea of blood sugar testing. But given that most of us spend a lot of the day -- maybe even most of the day -- having eaten something within the last few hours, can we really call the glucose levels we have after eating "abnormal"? In fact, isn't it more abnormal to go eight hours during the day without eating or drinking anything?

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In short, this is the idea behind postprandial -- or after-meal -- glucose testing. Since we spend so much time in a postprandial state, the argument goes, it's important to monitor blood glucose levels during that time, too. While it may make intuitive sense, postprandial testing is one of the most hotly debated subjects in diabetes care. Is it an important new way of testing blood glucose that will reshape diabetes treatment, or is it merely a distraction from what's really important?

Setting the Limits

Paul Jellinger, MD, past president of the American Association of Clinical Endocrinologists (AACE), is a firm believer in the importance of postprandial testing. In 2001, when Jellinger was president of AACE, the organization issued a consensus paper on diabetes treatment that discussed postprandial testing.

"What we came up with was a number of new guidelines for postprandial testing," Jellinger tells WebMD. "We made a recommendation that a person's postprandial blood sugar, taken two hours after eating, should not exceed 140 mg/dL."

How did they arrive at that limit? Given the ways in which we all eat, postprandial testing would seem inherently imprecise; for instance, the glucose level of someone who just ate a salad for lunch might be pretty different from someone who just finished a Thanksgiving dinner. To resolve this issue, the AACE set a cutoff based on a comparison of the typical glucose levels of diabetic and non-diabetic people after eating.

"We know that in a normal person without diabetes, it's very rare for his or her blood sugar to exceed 140 mg/dL two hours after a meal," says Jellinger. "It can happen, but not often."

However, Jellinger is quick to concede that the cutoff number has been contentious. Just because people without diabetes don't usually reach a blood-glucose level of more than 140 mg/dL does not necessarily mean that anything above that particular number increases the risks of diabetic complications.

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