(Regarding blood sugar standards) I heard to measure it ‘two hours after a meal’… Is that when I took my first bite? Or is it based on when I finished eating?

It is known that the standard time for measuring postprandial blood sugar is 'two hours after eating.' If it took longer than usual to eat, would the timing of the measurement change? A reader asked a question regarding postprandial blood sugar.

Meals usually take 30 to 40 minutes, but sometimes they take longer. When measuring post-meal blood sugar, should I take the time when I take my first bite, or when I finish the entire meal?

Q. When exactly should I measure post-meal blood sugar?

A. Measure two hours after the 'start' of the meal

Postprandial blood sugar should be measured two hours after the time you took your first bite. Although it varies depending on the type and amount of food consumed and the body's glucose metabolism, blood sugar levels are generally highest two hours after the start of a meal, so this is when you should measure it.

When glucose enters the bloodstream, the pancreas begins secreting insulin at its peak. Insulin continues to be secreted for one to two hours to lower the elevated blood sugar levels. After two hours, insulin secretion stops, and blood insulin levels drop. In other words, the entire process of glucose metabolism—including digestion, absorption, blood sugar elevation, and insulin secretion—is completed within two hours of a meal.

Since the peak of blood sugar levels following food intake occurs within two hours and then gradually decreases to approach the normal range, measurements must be taken at the point where blood sugar reaches its peak to check the body's ability to regulate blood sugar.

Even in situations where you dine for more than an hour, such as at a buffet or a multi-course restaurant, you should measure your blood sugar two hours after you begin eating. While the peak blood sugar level may vary depending on the amount of food consumed and the ratio of nutrients, it will not appear later than two hours after eating, no matter how late.

It is advisable to measure postprandial blood sugar regularly because it is necessary to track changes in blood sugar levels consistently. Diabetes tolerance tests and clinical studies have long used the 'two hours after a meal' standard for postprandial blood sugar measurement.