Blood sugar, or glucose, serves as the primary fuel used by the body tissues to generate the energy necessary to carry out their respective functions. The hormones insulin and glucagon control the blood sugar level through opposite mechanisms. Insulin lowers the blood sugar level and glucagon raises blood glucose concentration. Abnormally high or low blood sugar levels---hyperglycemia and hypoglycemia, respectively---disrupt body chemistry and cellular functions. These disruptions cause distinctive symptoms of a blood sugar imbalance.
Increased Thirst and Urination
An abnormally elevated blood sugar level has a diuretic effect on the kidneys, causing increased excretion of water. Patients with hyperglycemia, therefore, experience increased urinary frequency and volume, or polyuria. Excess loss of water through the kidneys commonly causes dehydration, triggering increased thirst, or polydipsia. Polyuria and polydipsia are hallmark symptoms of diabetes mellitus, notes "The Merck Manual for Healthcare Professionals."
Increased Appetite
Patients with hyperglycemia, especially those with Type 1 diabetes mellitus, often have an increased appetite, reports the University of Iowa Hospitals and Clinics. Hyperglycemia typically indicates a disruption in the delivery of glucose to the body tissues. Although the blood sugar concentration in the bloodstream remains elevated, little glucose reaches the sugar-starved body tissues. Through a cascade of chemical reactions, the brain receives the message that the body tissues need sugar and responds by increasing hunger signaling.
Tremors, Sweating, Anxiety and Racing Heartbeat
An abnormally low blood sugar level often triggers a release of the hormone epinephrine from the adrenal glands. The surge of "fight or flight" hormone in the bloodstream causes tremors, increased sweating, a racing heartbeat and anxiety, explains the medical information website InteliHealth.
Patients with long-standing diabetes may develop a complication known as hypoglycemia unawareness. In patients with this condition, a low blood sugar level fails to trigger adrenal gland release of epinephrine, points out the Joslin Diabetes Center. Without an epinephrine surge, patients do not experience tremors, sweating, a rapid heartbeat or anxiety as warning symptoms of a falling blood sugar level. Patients with hypoglycemia unawareness remain at high risk for episodes of severe hypoglycemia due to an inability to detect the condition.
Coma
Profoundly elevated or decreased blood sugar levels can lead to coma. Two hyperglycemic states, diabetic ketoacidosis and hyperglycemic hyperosmolar syndrome, may lead to coma without prompt treatment. The National Library of Medicine encyclopedia MedlinePlus notes that diabetic ketoacidosis most commonly occurs in patients with Type 1 diabetes mellitus, and hyperglycemic hyperosmolar syndrome occurs almost exclusively in patients with Type 2 disease. A progressively decreased level of consciousness precedes coma with both diabetic ketoacidosis and hyperglycemia hyperosmolar syndrome.
References
- The Merck Manual for Healthcare Professionals: Diabetes Mellitus, Symptoms and Signs
- University of Iowa Hospitals and Clinics: Hyperglycemia (High Blood Sugar)
- InteliHealth: Hypoglycemia
- Joslin Diabetes Center: What Can I Do to Prevent Serious Hypoglycemic Episodes When I Am Hypoglycemic Unaware?
- MedlinePlus: Diabetic Hyperglycemic Hyperosmolar Syndrome
