A detailed, accurate, balanced look at a physical symptom that is much misunderstood. Endocrinologist Bennion (Stanford School of Medicine) has no use for patients and physicians who won't try to understand that, first, hypoglycemia is simply low blood sugar. It is a symptom, not a disease; it has many different causes; it can cause other, related symptoms; most of these other symptoms can also have other causes. Consequently, there is only one valid way to tell if someone is hypoglycemic: measure the amount of sugar in the blood at the time an attack is being felt. Other medical tests--e.g., the glucose tolerance test--are not definitive; neither are hair analysis (a favorite of the orthomolecular school), personal ""symptom"" diaries, or even careful medical histories. If hypoglycemia turns out not to be present in blood tests, says Bennion, then the physician must track down another cause of the symptoms--and not lazily use hypoglycemia as a catchall diagnosis to pacify a worried patient. And if hypoglycemia is found, he warns, the cause must be found and treated; simple symptom relief is insufficient. Bennion covers all this thoroughly and with voluminous case studies. The going can be rough (""if only enough insulin is given to get the plasma glucose down to say 50 mg/dl, we cannot be sure we have truly produced hypoglycemia, and therefore cannot be sure we have stimulated the pituitary gland sufficiently. . .""); but readers who persevere--physicians or patients--will have a full, up-to-date grasp of this shadowy condition.