24-h Void number as an indicator of hydration status

J. M. Burchfield, M. S. Ganio, S. A. Kavouras, J. D. Adams, M. A. Gonzalez, C. B. Ridings, N. E. Moyen, M. A. Tucker

Research output: Contribution to journalArticlepeer-review

18 Scopus citations


Few user-friendly hydration assessment techniques exist for the general population to use on a daily basis. The present study evaluated void number over 24 h as a potential hydration assessment tool.Subjects/Methods:Male and female subjects collected urine for 24 h while adequately hydrated (n=44; 22±4 years, 168±16 cm, 73±15 kg) or fluid restricted (n=43; 22±3 years, 175±10 cm, 81±24 kg). As a control, participants were asked to void when feeling the 'first urge to void' on a commonly used urge scale and noted the volume of each void. For each sample, 24-h urine volume, osmolality (U OSM), specific gravity (U SG) and color were measured in the laboratory.Results:As designed, the level of urge upon voiding was consistent throughout the study (2±0; 'first urge to void'). Samples were classified by U SG as either euhydrated (U SG <1.020) or hypohydrated (U SG ≥1.020). Grouping by U OSM did not change results. Euhydrated versus hypohydrated individuals had greater 24-h urine volume (1933±864 versus 967±306 ml, respectively) and lower urine color (2±1 versus 5±1), U SG (1.012±0.004 versus 1.025±0.004) and U OSM (457±180 versus 874±175 mOsm/kg H 2 O; all P<0.001). Euhydrated individuals voided more than hypohydrated individuals over the 24-h period (5±2 versus 3±1 voids; P<0.001). Additionally, void number inversely correlated with hydration status as identified by U SG (r=-0.50; P<0.05) and U OSM (r=-0.56; P<0.05).Conclusions:In conclusion, over 24 h, individuals with a higher void number were euhydrated (that is, had less concentrated hydration biomarkers) than those with a lower void number. Based on these data, void number might be utilized as a simple and feasible hydration assessment for the general public, as it utilizes no equipment or technical expertise.

Original languageEnglish (US)
Pages (from-to)638-641
Number of pages4
JournalEuropean Journal of Clinical Nutrition
Issue number5
StatePublished - May 9 2015
Externally publishedYes

ASJC Scopus subject areas

  • Medicine (miscellaneous)
  • Nutrition and Dietetics


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