Hypoglycemia (hi-poe-gly-SEE-me-uh) is the medical term for low blood sugar. To some degree, you've probably experienced hypoglycemia at one time or another, when you've gone too long between meals. The sugar or starches in food are converted into glucose, which provides energy for your cells, especially the brain. When levels of glucose or blood sugar fall too low, typically under 60 milligrams per deciliter, you could feel the effects. Common signs of low blood sugar include fatigue, headache, trembling, weakness, sudden hunger, and crankiness. You could find it hard to concentrate, become sleepy, or lose your temper. Lack of food is what's responsible for most hypoglycemic (hi-poe-gly-SEE-mic) attacks. However, other factors can lower your blood sugar, such as drinking alcohol, or exercising vigorously. This can cause a dangerous drop in levels if you're diabetic, and already taking insulin or other medication to lower your blood sugar. Certain conditions of the liver, pancreas, or thyroid gland can also result in low blood sugar, but these are relatively rare. When it occurs in diabetics, hypoglycemia is a serious threat, and can even be fatal. If you're diabetic, be alert to symptoms, and always keep something sweet with you to eat in case of an emergency. For more information on hypoglycemia, speak with a doctor.