Common presenting symptoms include nausea, confusion, tremor, sweating, palpitations, or hunger. Patients may present with a nonspecific clinical history.
Documentation of a blood glucose <60 mg/dL with accompanying symptoms is crucial to diagnosing clinically significant hypoglycemia.
Important causes to consider are iatrogenic or factitious hypoglycemia secondary to insulin or sulfonylurea use. Another common cause may be physiological reactive hypoglycemia. However, the most worrisome causes are insulinoma and tumor-related hypoglycemia.
Preferred treatment for an insulinoma is surgical excision.
Hypoglycemia is a clinical syndrome present when the blood glucose concentration falls below the normal fasting glucose range, generally <60 mg/dL. When glucose values drop below the normal fasting range, glucose meters are not accurate and laboratory serum or plasma testing is useful to confirm the actual blood sugar value.  Whipple triad should be present in cases of true hypoglycemia: hypoglycemic symptoms, accompanying low blood glucose concentration, and resolution of symptoms after raising the blood glucose concentration to normal. 
This monograph covers non-diabetic hypoglycemia in adults.
Professor of Medicine
University of Iowa
Des Moines Internal Medicine Residency Training Program
Veterans Affairs Medical Center
UK is an author of a number of references cited in this monograph. UK declares that he has been a member of a speakers' panel and advisory board for Sanofi, and has received a research grant from this company.
Professor Udaya Kabadi would like to gratefully acknowledge Dr Steven Kunkel, a previous contributor to this monograph. SK declares that he has no competing interests.
Renal and Hypertension
Professor of Medicine
Division of Nephrology
Department of Medicine
Loyola University School of Medicine and Edward Hines Jr VA Medical Center
DJL declares that he has no competing interests.
Johns Hopkins University School of Medicine
SB declares that he has no competing interests.
Clinical Director/Clinical Lead for Diabetic Medicine
King’s College Hospital NHS Foundation Trust
DH declares that he has no competing interests.
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