Urine colour change as an indicator of change in daily water intake: a quantitative analysis

PURPOSE: Urine colour (U(Col)) is simple to measure, differs between low-volume and high-volume drinkers, and is responsive to changes in daily total fluid intake (TFI). However, to date, no study has quantified the relationship between a change in TFI and the resultant change in U(Col). This analysis aimed to determine the change in TFI needed to adjust 24-h U(Col) by 2 shades on an 8-colour scale, and to evaluate whether starting U(Col) altered the relationship between the change in TFI and change in U(Col). METHODS: We performed a pooled analysis on data from 238 healthy American and European adults (50 % male; age, 28 (sd 6) years; BMI 22.9 (sd 2.6) kg/m(2)), and evaluated the change in TFI, urine volume (U(Vol)), and specific gravity (U(SG)) associated with a change in U(Col) of 2 shades. RESULTS: The mean [95 % CI] change in TFI and U(Vol) associated with a decrease in U(Col) by 2 shades (lighter) was 1110 [914;1306] and 1011 [851;1172] mL/day, respectively, while increasing U(Col) by 2 shades (darker) required a reduction in TFI and U(Vol) of −1114 [−885;−1343] and −977 [−787;−1166] mL/day. The change in U(Col) was accompanied by changes in U(SG) (lighter urine: −.008 [−.007;−.010]; darker urine: +.008 [.006;.009]). Starting U(Col) did not significantly impact the TFI change required to modify U(Col) by 2 shades. CONCLUSIONS: Our results suggest a quantifiable relationship between a change in daily TFI and the resultant change in U(Col), providing individuals with a practical means for evaluating and adjusting hydration behaviours.