Pseudohypoglycemia: A Simple Approach to Complex Phenomenon

Background: Pseudohypoglycemia is a condition where the measured glucose level is falsely lower than the actual level. It can be due to impaired circulation or in vitro glycolysis. Clinical Case: Patient 1: A 58-year-old male with a past medical history of sickle cell trait was admitted for alcohol intoxication. Low blood glucose levels were found on finger stick point-of-care testing (POCT). Fasting and postprandial glucose levels were between 17 and 60 mg/dL. The patient was asymptomatic, alert with no tremor, palpitation, or sweating. Glucose POCT was repeated from the earlobe each time a low finger stick level was found, showing normal glucose levels ranging between 85 to 115 mg/dL, confirmed with venous blood glucose measurement. On examination, the patient had mild skin thickening of the hands, with no acrocyanosis, calcinosis, or finger ulceration—normal peripheral pulses with no signs of heart failure. Lab results showed macrocytic anemia, otherwise normal metabolic panel. ANA, anti-Scl-70, and anticentromere antibodies were negative. Patient 2: A 91-year-old female admitted for decompensated heart failure was incidentally found to have fasting glucose levels on finger stick POCT ranging between 30–50 mg/dL. Postprandial glucose on finger stick POCT was ranging between 55–120 mg/dL. Venous glucose levels were ranging between 90 and 180 mg/dL. The patient was alert and asymptomatic. Examination showed bilateral acrocyanosis, poor peripheral circulation with capillary refill > 5 seconds, pitting pedal edema, elevated JVP, and crackles on chest auscultation. Labs showed BNP levels of 1130 pg/mL (n < 100 pg/mL), with ejection fraction of about 35% on echocardiography. Heart failure management was optimized, and warming of the hands with blankets improved peripheral circulation, with capillary refill < 2 seconds, and resolution of cyanosis coinciding with matching of finger stick POCT glucose levels to that of venous blood. Both patients were asymptomatic at the time of low POCT glucose and thus did not fulfill Whipple’s triad (measured hypoglycemia, symptomatic, a reversal of symptoms on glucose administration). Furthermore, they had no history of diabetes or the use of any hypoglycemic agents. Thus, normal venous blood glucose levels documented at the time of low POCT glucose lead to a diagnosis of pseudohypoglycemia. The etiology in patient 1 was likely due to peripheral vascular disease. In patient 2, the cause was likely due to congestive heart failure, with poor peripheral perfusion. Clinical Lesson: Low glucose levels are frequently encountered in clinical practice. It is essential to check if the non-diabetic patient is symptomatic or not. It is worth checking glucose levels from other sites in asymptomatic patients who do not fulfill Whipple’s triad before preceding into an elaborate hypoglycemia work-up.