PURPOSE OF REVIEW: The purpose of the review is to provide recommendations to improve clinical decision-making based on the strengths and weaknesses of commonly used hydration biomarkers and clinical assessment methods.

RECENT FINDINGS: There is widespread consensus regarding treatment, but not the diagnosis of dehydration. Even though it is generally accepted that a proper clinical diagnosis of dehydration can only be made biochemically rather than relying upon clinical signs and symptoms, no gold standard biochemical hydration index exists. Other than clinical biomarkers in blood (i.e., osmolality and blood urea nitrogen/creatinine) and in urine (i.e., osmolality and specific gravity), blood pressure assessment and clinical symptoms in the eye (i.e., tear production and palpitating pressure) and the mouth (i.e., thirst and mucous wetness) can provide important information for diagnosing dehydration.

SUMMARY: We conclude that clinical observations based on a combination of history, physical examination, laboratory values, and clinician experience remain the best approach to the diagnosis of dehydration.