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A lavatory urine color (LUC) chart method can identify hypohydration in a physically active population



To provide a new and efficient at-the-toilet-bowl method of self-assessing urine concentration via urine color (Uc) to identify hypohydration.


A large athletic population (n = 189) delivered a urine sample, then chose a color panel that was displayed on the back wall of the lavatory stall. Selection was based on duration of urine voiding time, so that for a short-duration, the lighter panel was selected; for a mid-duration, the mid color panel; and for a longer-void-duration, the darker panel was selected. Then, subjects noted if their urine was lighter than, similar to, or darker than the selected color panel. Trained investigators also rated subjects’ urine samples. To assess validity of Uc classification, the outcome was compared with a urine concentration (urine specific gravity, USG, and urine osmolality) threshold indicating hypohydration.


Urine color was scored similarly by subjects and investigators (P = 0.99). Based on receiver operating curves (ROC), the method scored fair, i.e., the area under the curve ranging 0.73–0.82, with an accuracy of participants and investigators correctly classifying 72% and 75% urine samples compared to a USG threshold of 1.020, respectively, and 62% and 70% compared to a urine osmolality threshold of 836 mmol·kg−1, respectively.


This new lavatory urine color (LUC) method of scoring Uc levels to assess potential hypohydration gives results similar to those of traditional urine color charts, but it has the advantage of an immediate assessment of hydration status based on scoring urine color directly from the toilet bowl.

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We thank all participants. We also thank the student helpers of the Athleat Field Lab with the data collection: Brooke Butterick, Rebecca Mrotek, Gabriel Gonzales, Darya Youssefi, Jensen Skinner, Katie Pesek, Deanna Driss, Scott Armistead, Yat Chan, Caitlyn Donnelly, Kayla Rasmussen, Sarah Fagus, Maryam Nalbandian, Kayla Lundy, Ann Provencio and Alexandra Williams. Finally we want to thank Terry Christenson for his critical feedback on the manuscript.


The study was funded by the Global Sport Institute at Arizona State University.

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The study was designed by FW and DB; data were collected by DT, KV and FW; data were analysed by DT and FW; data interpretation and manuscript preparation were undertaken by FW, DT, KV, and DB. All authors approved the final version of the paper.

Corresponding author

Correspondence to Floris C. Wardenaar.

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Conflict of interest

None of the authors have any commercial conflicts of interest to disclose.

Ethical approval

All study procedures were approved by the Institutional Review Board at Arizona State University (STUDY00010071).

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At the start of the experiment, participants signed giving their informed consent.

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Wardenaar, F.C., Thompsett, D., Vento, K.A. et al. A lavatory urine color (LUC) chart method can identify hypohydration in a physically active population. Eur J Nutr 60, 2795–2805 (2021).

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  • Self-assessment
  • Hydration status
  • Osmolality
  • Urine specific gravity
  • USG