Study objective: To assess the value of plasma glucose concentration alone as a predictor of neurologic dysfunction in nondiabetic subjects with normal baseline neurologic examination and electroencephalographic (EEG) findings. Methods: Neurologic function and EEG results were evaluated in 17 subjects before and during insulin-induced hypoglycemia using relevant and reliable clinical tools for bedside use. Results: Hypoglycemia (mean nadir concentration, 30 mg/dL) was without effect on level of consciousness or cranial nerve, motor, sensory, vestibulocerebellar, language, or simple visuospatial functions. Attention was minimally impaired in all subjects, but memory in only 3. EEG results remained normal in 5 subjects; minimal to moderate nonspecific changes occurred in the rest. All patients manifested signs of sympathetic stimulation from hypoglycemia, including tremor, tachycardia, and diaphoresis. The manifestations of neuroglycopenia did not correlate significantly with nadir plasma glucose or duration of hypoglycemia. Conclusion: Moderately severe hypoglycemia of short duration can be neurologically occult, or subtle inattention can be its first and only clinical manifestation. Our findings are at variance with reports in the emergency medicine literature in which marked deficits are universally present at glucose concentrations equal to those attained in this study. This discrepancy suggests that the expression of neuroglycopenia is multifactorially determined and that plasma glucose concentration alone does not predict neurologic dysfunction in nondiabetic subjects with normal baseline neurologic examinations. [Osorio I, Arafah BM, Mayor C, Troster AI: Plasma glucose alone does not predict neurologic dysfunction in hypoglycemic nondiabetic subjects. Ann Emerg Med March 1999;33:291-298.]