Physiologic basis for understanding quantitative dehydration assessment

Am J Clin Nutr. 2013 Mar;97(3):455-62. doi: 10.3945/ajcn.112.044172. Epub 2013 Jan 23.


Dehydration (body water deficit) is a physiologic state that can have profound implications for human health and performance. Unfortunately, dehydration can be difficult to assess, and there is no single, universal gold standard for decision making. In this article, we review the physiologic basis for understanding quantitative dehydration assessment. We highlight how phenomenologic interpretations of dehydration depend critically on the type (dehydration compared with volume depletion) and magnitude (moderate compared with severe) of dehydration, which in turn influence the osmotic (plasma osmolality) and blood volume-dependent compensatory thresholds for antidiuretic and thirst responses. In particular, we review new findings regarding the biological variation in osmotic responses to dehydration and discuss how this variation can help provide a quantitative and clinically relevant link between the physiology and phenomenology of dehydration. Practical measures with empirical thresholds are provided as a starting point for improving the practice of dehydration assessment.

Publication types

  • Review

MeSH terms

  • Blood Volume / physiology
  • Body Water / physiology
  • Dehydration*
  • Humans
  • Neurophysins / metabolism
  • Osmolar Concentration
  • Protein Precursors / metabolism
  • Thirst / physiology
  • Vasopressins / metabolism
  • Water-Electrolyte Balance


  • AVP protein, human
  • Neurophysins
  • Protein Precursors
  • Vasopressins