Pseudohypoglycemia: a cause for unreliable finger-stick glucose measurements.

OBJECTIVE: To identify patients with an inaccurate diagnosis of hypoglycemia and discuss predisposing factors.

METHODS: We describe our patient's clinical presentation, laboratory work-up, hospital course, and follow-up and review similar cases from the literature.

RESULTS: A 27-year-old woman with Raynaud phenomenon was admitted because of symptomatic hypoglycemia. Physical examination showed tremulousness, sweating, and the classic Raynaud color changes of the hands during episodic symptoms. A 72-hour fast revealed finger-stick capillary glucose values ranging from 32 to 45 mg/dL on multiple occasions, while concurrent plasma glucose values were consistently 1.5 to 2 times higher. Capillary measurements of glucose performed in the arms and legs at room temperature and after warming of each extremity disclosed an increase in glucose levels from a range of 35 to 52 mg/dL at room temperature to a range of 82 to 100 mg/dL after warming, confirming a discordance between capillary and venous blood results. The diagnosis of pseudohypoglycemia was made. Pseudohypoglycemia has been reported in patients with Raynaud phenomenon, peripheral vascular disease, and shock and may result from increased glucose extraction by the tissues because of low capillary flow and increased glucose transit time.

CONCLUSION: Pseudohypoglycemia should be suspected in the setting of impaired microcirculation and can be confirmed by readily available means.