Elevated blood sugar, or hyperglycemia, is a condition in which an excess amount of glucose circulates in the blood. Although chronic levels of glucose in the blood after a period of fasting that exceed 125 mg/dl (normal levels are 80 to 100 mg/dl) may lead to a sustained hyperglycemic state, chronic hyperglycemia results in complications associated with diabetes, while temporary hyperglycemia is generally benign.
Insulin is a hormone secreted by the pancreas that allows cells to take up glucose from the blood. Chronic hyperglycemia usually leads to a diagnosis of diabetes due to a malfunctioning insulin response. Tissues may become unresponsive to the hormone--a condition typical of type 2 diabetes--or cells in the pancreas responsible for producing the hormone may be nonfunctional, which characterizes type 1 diabetes.
Temporary hyperglycemia is a physiological response to lifestyle habits.
Diet
Certain foods, generally carbohydrates, that break down quickly during digestion and release glucose rapidly into the bloodstream produce large spikes in blood sugar levels. In 1981 a study published in the "American Journal of Clinical Nutrition" defined the glycemic index of a food as the area under the two-hour blood glucose response curve following the ingestion of a fixed portion of carbohydrate--usually 50g. The higher the glycemic index of a food, the higher and faster the spike in the blood sugar levels. Foods high on the glycemic index include sugary cereals, baked potatoes, white bread and white rice, and even watermelon.
Illness or Infection
High blood glucose is also a common problem encountered in critically ill or hospitalized patients. According to a study published in the "Critical Care Clinics" journal in January 2001, in prolonged illnesses, less insulin is released due to a suppression of other signals that normally promote its release from the pancreas. Less insulin in the bloodstream leads to a decreased uptake of glucose by cells and a higher blood glucose level. The reason for this phenomenon is to support the energy needs of glucose-dependent organs such as the brain, adrenal medulla, and red blood cells. The presence of counterregulatory hormones that increase blood sugar, such as glucagon, as well as high circulating or tissue levels of cytokines that help the body fight an infection lead to "stress hyperglycemia."
High Intensity Exercise
An article published by the American Diabetes Association in 2002 states that intense exercise leads to a state in which the body is considered to be in a high stress mode through which increased blood glucose levels serve as a physiologic response to maintain energy reserves. During high intensity exercise, insulin-mediated glucose uptake is reduced.
Inactivity
Low intensity exercise reduces blood sugar levels over time. According to the MayoClinic.com, regular physical activity uses up glucose as energy and makes cells more sensitive to insulin. According to the American Diabetes Association, glucose concentrations in the blood were reduced after low-intensity exercise when compared with those who did not engage in physical activity.
Medications
According to a study published in the Oct. 24, 2001 "Journal of the American Medical Association," certain types of medications may contribute to elevated blood glucose levels. These include beta blockers, niacin, thiazide diuretics, protease inhibitors, corticosteroids, stimulants such as epinephrine, as well as certain antipsychotic drugs.
References
- "Journal of the American Medical Association"; Drug-Induced Hyperglycemia; Beatriz Luna, PharmD, Mark N. Feinglos, MD, CM; Oct. 24, 2001
- "American Journal of Clinical Nutrition"; Glycemic index of foods: a physiological basis for carbohydrate exchange. Jenkins D, Wolever T, Taylor R, et al. 1981.
- "Critical Care Clinics." Stress-Induced Hyperglycemia. K. McCowen et. al.; January 2001.
- "Diabetes"; Intense Exercise Has Unique Effects on Both Insulin Release and Its Roles in Glucoregulation; Errol B. Marliss, Mladen Vranic; 2002.
- MayoClinic.com: Pre-Diabetes - Risk Factors
