Dear Diabetes: What is postprandial glucose and why does it matter?
First off, prandial is a word meaning “mealtime.” So postprandial glucose (PPG) refers to the concentration of glucose (sugar) in the blood after a meal has been eaten. In order to understand postprandial glucose and why it matters, it’s helpful to understand metabolism, or what happens as the body converts carbohydrates into the glucose that cells use as fuel.
The human body generally requires blood glucose levels to stay within a relatively narrow range: Too much glucose can result in hyperglycemia; not enough can lead to hypoglycemia.
Normally, blood sugar levels are kept within a healthy range by the activity of two hormones: insulin and glucagon. When a meal is consumed, the blood sugar level increases as the body converts the digestible carbohydrates into glucose. As this glucose enters the bloodstream, the pancreas responds by making the hormone insulin, which prompts cells to take the glucose out of the blood and use it (or store it for later use) as energy.
As glucose leaves the bloodstream to be consumed by cells, the pancreas begins to secrete a second hormone, glucagon, which activates the liver to release stored glucose. This balance of insulin and glucagon keeps a steady supply of glucose available for cells to use as energy.
What happens to glucose levels after a meal?
As the body metabolizes carbohydrates, glucose levels begin to rise. The specific level may be affected by a number of factors, including the amount of carbohydrates in the meal, how long it takes to eat the meal and how much is consumed during the mealtime.
People who do not have diabetes generally experience a peak in post-prandial glucose about an hour after beginning a meal, usually below 120 mg/dl and rarely above 140 mg/dl. Their PPG returns to pre-meal levels within two to three hours. However, even though PPG levels have returned to pre-meal levels, carbohydrates are still being absorbed for up to six hours after a meal. PPG levels are determined by carbohydrate absorption, the body’s insulin and glucagon secretion, and their coordinated effects on glucose metabolism.
In people living with type 1 diabetes, the pancreas no longer makes insulin. People living with type 2 diabetes don’t make enough insulin, or their bodies become unable to properly respond to it. The American Diabetes Association recommends a target postprandial glucose level of below 180 mg/dl for all those living with diabetes. (By contrast, the Association recommends a before meal, or “fasting” glucose level between 80 and 130 mg/dl.)
Postprandial glucose and A1C
People living with diabetes might also hear about postprandial glucose levels in relation to their A1C. An A1C test (also referred to as an HbA1c or glycohemoglobin test) measures a person’s average blood glucose levels over the previous two to three months, and may help assess how well a treatment plan is working.
American Diabetes Association Standards of Medical Care – 2016 recommends an A1C goal of less than 7% (154 mg/dl) for most nonpregnant adults. A doctor may adjust this goal for a specific person, based on a number of factors, including the person’s overall health and/or their risk for complications.
Current research suggests that A1C levels may be determined by both postprandial glucose levels and fasting glucose levels. Some people living with diabetes may not achieve their target A1C goals, even if they are meeting their fasting glucose level target.
A person’s primary care physician or other appropriate member of their diabetes care team may recommend a postprandial glucose test. Tests that measure PPG are given two hours after the start of a meal.
If your doctor has ordered an A1C test and your levels are not within the target range, your doctor may work with you to develop a treatment plan to help achieve your diabetes management goals.
© 2016 The DX: The Diabetes Experience