A rise in blood glucose levels is normal after eating a meal, particularly a meal loaded with carbohydrates. People who have diabetes will have higher spikes in blood glucose--and for longer periods.
Carbohydrates convert to glucose in the bloodstream. The pancreas secretes insulin, which bonds with the blood glucose to supply the body with energy. Someone with diabetes either has an insufficient supply of insulin or the body does not process the insulin efficiently, resulting in too much glucose in the bloodstream.
Normal blood glucose levels are 70 mg/dl to 120 mg/dl (milligrams of glucose to deciliters of blood). A blood glucose level above 120 mg/dl could result in a condition known as hyperglycemia--high blood sugar.
Postprandial blood glucose levels, or blood glucose levels after eating a meal, should be 120 mg/dl two hours after the start of a meal for healthy people. The National Diabetes Information Clearinghouse states that someone with diabetes could see blood glucose levels as high as 180 mg/dl one to two hours after the start of a meal.
The rise in blood glucose levels after eating is directly related to the amount and types of carbohydrates included with the meal.
If postprandial blood glucose levels are consistently higher than 120 mg/dl two hours after the meal, diabetes, pre-diabetes or insulin resistance might be indicated. Consult your physician for testing and diagnosis.