Whenever you eat anything containing carbohydrates, your digestive system breaks those molecules down into simple glucose and passes them to the bloodstream. From there, your body can utilize these sugars to provide energy and fuel fundamental bodily functions. However, a diet too high in carbohydrates can cause glucose to build up in your bloodstream, leading to a dangerous condition called hyperglycemia.
Insulin
When your body detects an increase in blood sugar, your pancreas releases a hormone called insulin. Insulin stimulates cells and organs like your liver, causing them to absorb this excess glucose and either utilize it for energy or store it for later use. This reaction is important, because it both regulates the body's ability to gain energy from carbohydrates as well as protects the body from an excess of sugar in the blood.
Normal Response
Blood glucose tests usually express the concentration of sugar in milligrams per deciliter of blood. According to the American Diabetes Association, the normal range for fasting glucose is 70 to 130 mg/dl, and the normal limit for blood sugar after a meal is 180 mg/dl, with a return to fasting levels in a few hours. Under normal circumstances, blood sugar levels will fluctuate between these extremes as your digestive system breaks down carbohydrates and insulin works to lower blood sugar levels after eating.
Insulin Resistance
Over time, a diet high in carbohydrates can cause the pancreas to release large amounts of insulin into the bloodstream. Constant exposure to high doses of the hormone can cause your cells to become resistant to its effects, impairing your body's ability to effectively deal with blood glucose levels. If this condition continues to worsen, it can develop into type 2 diabetes. Often, the first sign of this problem is elevated blood glucose levels after a meal.
Glucose Testing
If you are beginning to undergo the effects of insulin resistance, your blood glucose levels may spike higher after a meal than normal, and will take longer to come down to normal levels. Your doctor may measure your insulin response through an oral glucose tolerance test, in which you will drink a glucose solution and then test your blood two hours later. A normal response is for blood glucose to drop to 140 mg/dl or lower, according to the American Diabetes Association. Higher numbers indicate insulin resistance or prediabetes, with a high of 200 mg/dl or more warranting a diagnosis of type 2 diabetes.
Hyperglycemia
If your blood sugar does not return to normal levels after a meal, it can cause a number of problems. If cells cannot utilize sugar for fuel, the body will attempt to break down fats in a process called ketosis. This can lead to weight loss, but the byproducts of ketosis can cause stress and damage to your kidneys, and if left untreated can cause you to fall into a coma. In addition, the inability of white blood cells to use glucose for fuel impairs their ability to protect you, rendering you open to opportunistic infections.
