Evaluation of Asymptomatic Fasting Hypoglycemia in Outpatients Without Diabetes.

Background: There are no studies on the clinical significance of asymptomatic hypoglycemia detected incidentally during routine testing.

Methods: Baseline fasting serum glucose was determined in 1333 individuals without diabetes (43.3% males, median age 50 years, range 18 to 91 years) to investigate the prevalence of hypoglycemia (fasting serum glucose <70 mg/dL) and the associated demographic, lifestyle, and metabolic factors. Individuals with baseline hypoglycemia were followed (median follow-up, 8.7 years) and assessed for hypoglycemia symptoms. Seven-day continuous glucose monitoring was performed in a subsample of 489 individuals.

Results: Baseline hypoglycemia was observed in 20 individuals (weighted prevalence, 1.58%, 95% confidence interval 0.87%-2.28%). Hypoglycemia was mild and asymptomatic in all cases (median, 67 mg/dL, range 63 to 69 mg/dL). The characteristics of those with hypoglycemia were similar to those with fasting serum glucose 70 to 80 mg/dL. Hypoglycemia was associated with female sex, younger age, and a more favorable metabolic profile (lower body mass index, glycohemoglobin and insulin resistance) than individuals with fasting serum glucose >80 mg/dL. Individuals with baseline hypoglycemia showed no distinct hypoglycemia features in continuous glucose monitoring (n = 9). During follow-up (n = 19), hypoglycemia in routine determinations, always mild, recurred in 42.1% of individuals, although the mean of successive glucose concentrations was higher than baseline in all cases. None of the individuals had symptoms that could constitute Whipple's triad (low serum glucose, symptoms of hypoglycemia, and symptomatic improvement after correction of hypoglycemia) during the follow-up period.

Conclusions: Detection of asymptomatic, mild hypoglycemia in routine blood tests is not indicative of disease and does not require further investigation.