Low blood glucose

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Author: Mikael Häggström [notes 1]
If called after hours about a low blood glucose value, inquire about:

  • 2 patient identifiers (for example name and date of birth).
  • Any symptoms of hypoglycemia if known.
  • Time of collection and time of collection by the lab.
  • If delayed more than 4 hours, it is generally a false low blood glucose if there is no report of hypoglycemia signs, and the lab can generally be told to hold the release of the result, and the absence of centrifugation at the time of collection can be confirmed with the blood drawing site the following day. For each hour before centrifugation, plasma glucose decreases by approximately 0.3 mmol/L, 6 mg/dL or 7% per hour, and serum glucose by approximately 0.25 mmol/L, 4.5 mg/dL or 5% per hour.[1]
  • For test results not sent out due to pre-analytical errors, preferably contact the clinician currently in charge of the patient to:
  • Exclude the presence of any symptoms expected in the case of an actual deranged value.
  • Inform about a cancelled test result, potentially with the need to take new samples.


  1. For a full list of contributors, see article history. Creators of images are attributed at the image description pages, seen by clicking on the images. See Patholines:Authorship for details.

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  1. Chris Higgins. Preanalytic error in plasma/serum glucose measurement examined. July 2019. In turn citing: Lippi G, Salvagno G, Lampus S et al. Impact of blood cell counts and volumes on glucose concentration in uncentrifuged serum and lithium-heparin blood tubes. Clin Chem Lab Med 2018; 56: 2125-31