Do you remember the story of "Goldilocks and the Three Bears," how she wanted things just right? Your body has the same approach to its regulation of blood sugar, always working to keep it just right. Your blood sugar level normally varies within a narrow range throughout the day, thanks to the intricate interplay among glucose-regulating hormones. The moderate rise in blood sugar that occurs after eating normally dissipates within a few hours and your blood sugar returns to a fasting level.
Normal Glucose Response
When you eat a carbohydrate-containing meal, the digested sugars enter your bloodstream from your small intestine. A corresponding rise in your blood sugar triggers increased release of the hormone insulin from your pancreas. Insulin facilitates the transfer of sugar from your bloodstream to your muscles, liver and other tissues. As your blood sugar level falls in response insulin, your pancreas slows its rate of secretion. The time required for your blood sugar to return to a fasting level after eating varies, depending on factors such as the nutritional composition of the meal and how quickly it passes from your stomach into your small intestine.
Impaired Glucose Tolerance and Diabetes
Medical professionals refer to an abnormal metabolic response to rising blood sugar levels as impaired glucose tolerance, or IGT. Markedly impaired glucose tolerance with blood sugar levels above specified thresholds means you have diabetes mellitus. A prolonged and abnormally steep rise in your blood sugar level after eating is a key feature of IGT and diabetes. This occurs because your cells do not respond normally to insulin, as occurs with type 2 diabetes, or your pancreas does not produce enough insulin, the hallmark feature of type 1 diabetes. With IGT or uncontrolled diabetes, your blood sugar may not return to a fasting level between meals. Additionally, your fasting blood sugar level may be abnormally elevated.
Hypoglycemic Response
Your body utilizes several mechanisms to prevent your blood sugar from falling to an abnormally low level, a condition termed hypoglycemia. Reactive or nutritional hypoglycemia describes a symptomatic fall in your blood sugar within four hours after eating. With this condition, your blood sugar drops below the fasting level to a concentration that causes symptoms, including paleness, irritability, confusion, and dizziness. Reactive hypoglycemia occurs rarely in otherwise healthy people and the cause remains controversial. Your doctor may advise you to eat small amounts of complex carbohydrates throughout the day and avoid simple sugars to control the problem.
Normal Fasting Blood Sugar
A normal fasting blood sugar is 70 to 99 mg/dL. A fasting blood sugar of 100 to 125 mg/dL suggests impaired glucose tolerance. A fasting blood sugar is 126 mg/dL or higher may indicate you have diabetes. Your doctor will likely run other tests, such as a hemoglobin A1c or a glucose tolerance, to confirm or rule out the diagnosis of diabetes.
References
- MedBio.info: Control of Blood Sugar Levels; Robert S. Horn, Ph.D.; March 2010
- "The Diabetes Answer Book: Practical Answers to More Than 300 Top Questions"; David K. McCulloch, M.D.; 2008
- MedBio.info: Insulin and Glucagon; Robert S. Horn, Ph.D.; December 2009
- "Practical Clinical Biochemistry: Methods and Interpretations"; Ranjna Chawla, Ph.D.; 2003
- HealthLinkBC: Eating Guidelines for Reactive Hypoglycemia; October 2008
- "Endocrine Practice"; American Association of Clinical Endocrinologists Medical Guidelines for Clinical Practice for Developing a Diabetes Mellitus Comprehensive Care Plan; Yehuda Handelsman, M.D., et al.; March--April 2011
