“Hypoglycemia” is the medical term for low blood sugar (glucose).

Occasionally, hypoglycemia can be dangerous (for example, from injecting too much insulin). It may also indicate a serious underlying medical condition, such as a tumor of the pancreas or liver disease. More often, however, when people say they have hypoglycemia, they are describing a group of symptoms that occur when the body overreacts to the rise in blood sugar that occurs after eating, resulting in a rapid or excessive fall in the blood sugar level. This is sometimes called “reactive hypoglycemia.”

Many people who believe they have reactive hypoglycemia do not, in fact, have low blood sugar levels,¹ and many people who do have low blood sugar levels do not have any symptoms of reactive hypoglycemia.² Some evidence suggests that reactive hypoglycemia may be partly a psychological condition.³ Consequently, some doctors believe that reactive hypoglycemia does not exist.⁴ Most doctors, on the other hand, have found reactive hypoglycemia to be a common cause of the symptoms listed below.