1. An abnormally low blood sugar usually resulting from excessive insulin or a poor diet.
2. An abnormally low level of glucose in the blood.

The symptoms of hypoglycemia may include anxiety, sweating, tremor, palpitations, nausea, and pallor.

Hypoglycemia also starves the brain of glucose energy, which is essential for proper brain function. Lack of glucose energy to the brain can cause symptoms ranging from headache, mild confusion, and abnormal behavior, to the loss of consciousness, seizure, and coma. Severe hypoglycemia can cause death.