A multidisciplinary consensus on dehydration: definitions, diagnostic methods and clinical implications

Jonathan Lacey, Jo Corbett, Lui Forni, Lee Hooper, Fintan Hughes, Gary Minto, Charlotte Moss, Susanna Price, Greg Whyte, Tom Woodcock, Michael Mythen, Hugh Montgomery

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Background: Dehydration appears prevalent, costly and associated with adverse outcomes. We sought to generate consensus on such key issues and elucidate need for further scientific enquiry.

Materials and methods: A modified Delphi process combined expert opinion and evidence appraisal. Twelve relevant experts addressed dehydration’s definition, objective markers and impact on physiology and outcome.

Results: Fifteen consensus statements and seven research recommendations were generated. Key findings, evidenced in detail, were that there is no universally accepted definition for dehydration; hydration assessment is complex and requires combining physiological and laboratory variables; “dehydration” and “hypovolaemia” are incorrectly used interchangeably; abnormal hydration status includes relative and/or absolute abnormalities in body water and serum/plasma osmolality (pOsm); raised pOsm usually indicates dehydration; direct measurement of pOsm is the gold standard for determining dehydration; pOsm >300 and ≤280 mOsm/kg classifies a person as hyper or hypo-osmolar; outside extremes, signs of adult dehydration are subtle and unreliable; dehydration is common in hospitals and care homes and associated with poorer outcomes.

Discussion: Dehydration poses risk to public health. Dehydration is under-recognized and poorly managed in hospital and community-based care. Further research is required to improve assessment and management of dehydration and the authors have made recommendations to focus academic endeavours.
Original languageEnglish
Number of pages20
JournalAnnals of Medicine
Early online date17 Jun 2019
Publication statusEarly online - 17 Jun 2019


  • dehydration
  • osmolar concentration
  • body fluid compartments
  • consensus
  • body water
  • water-electrolyte balance


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