Low blood sugar, or glucose, medically called hypoglycemia, occurs when levels of glucose in the blood fall below normal levels of 70 to 110 milligrams per deciliter, or mg/dL. Initial symptoms of hypoglycemia, which usually don't appear until blood glucose drops to 60 mg/dL, the Merck Manual reports, include shakiness, sweating, heart palpitations and hunger. As blood glucose continues to fall, confusion, slurred speech, blurred vision, seizures and coma can ensue. Hypoglycemia usually occurs in diabetics, but it can occur under other circumstances.
Diabetic Medications
Many diabetics take medications such as insulin to reduce abnormally high blood glucose levels. Insulin helps cells absorb glucose. If a person takes too much insulin or doesn't eat enough food after taking insulin, too much glucose is absorbed and the person develops hypoglycemia. Exercising, which burns glucose, after taking insulin can also cause hypoglycemia, MayoClinic.com explains.
Fasting
Prolonged fasting for more than eight hours may cause blood sugar levels to fall in some people, especially if combined with heavy drinking or strenuous exercise. Drinking without eating blocks release of glucose from the liver, according to MayoClinic.com. People with liver disease, which decreases the glucose stores in the liver, may develop hypoglycemia if they don't eat, the Merck Manual states.
Other Medications
Medications other than insulin can cause drops in blood glucose in some people. Drugs that can cause hypoglycemia include beta blockers, often used to treat high blood pressure; quinine, used to treat malaria and leg cramps; Bactrim, an antibiotic; and haloperidol, used for sedation, Drexel University School of Medicine explains.
Tumors
Certain tumors of the pancreas can cause an increase in insulin production, which can lead to hypoglycemia. Other tumors can produce insulin-like substances or use up too much glucose, also causing hypoglycemia, MayoClinic.com says.
Reactive Hypoglycemia
People who eat a meal heavy in carbohydrates may experience a rise in glucose level, followed by a sudden fall. Called reactive hypoglycemia, this form of low blood sugar is considered to be rare, according to the Merck Manual. Reactive hypoglycemia also may occur in people who have had gastric bypass surgery when too much insulin is released after eating.
Addison's Disease
Addison's disease, an autoimmune disease which destroys the adrenal glands, can cause hypoglycemia by lowering production of cortisol and aldosterone, Johns Hopkins Autoimmune Disease Research Center states. Addison's disease affects between one and six people per 100,000 and affects men and women equally.
