A 63-year-old man with metastatic lung cancer admitted for severe hip pain and malaise was noted to have erratic daily morning plasma glucose concentrations, with several critical values below 40 mg/dL (<2.2 mmol/L). Each time he had a critically low laboratory glucose value, a point-of-care finger-stick glucose was found to be within reference intervals. The remaining chemistry results were notable for occasional mild hypocalcemia and hypophosphatemia. He exhibited no clinical signs of hypoglycemia and work-up for infection was negative.


  1. Which values are likely correct, the finger-stick glucose or the plasma glucose?
  2. What can cause falsely low plasma glucose?
  3. What can be done to prevent the falsely low glucose measurements?
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