Purpose: Understanding the importance of euhydration in humans in order to ensure good health in various situations, the purpose of this review is to examine the available techniques in assessing hydration status.
Recent findings: During the past 20 years, many indices have been developed to assess hydration levels accurately in humans. Changes in body weight, haematological and urine parameters, bioelectrical impedance, skinfold thickness, heart rate and blood pressure changes are among these indices. Plasma osmolality, urine osmolality and urine specific gravity are the most widely used markers of hydration. However, urine colour has also been used with reasonable accuracy when laboratory analysis is not available or when a quick estimate of hydration is necessary. Some data indicate that urine colour is as good indicator of hydration as plasma or urine osmolality or urine specific gravity.
Summary: Although there is no 'gold standard' for assessment of hydration status, it appears that changes in body weight, along with urine osmolality, specific gravity, conductivity and colour are among the most widely used indices. Furthermore, they provide reasonable results, especially when the analysis is based on the first morning urine sample.