Fluid hydration status correlates with fatigue in multiple sclerosis (MS), according to a new study of 50 women with MS. Patients with good hydration status (defined by urine-specific gravity (USG) <1.015) reported lower fatigue scores on Fatigue Performance Scale than did patients with low hydration status (USG >1.015). Moreover, USG correlated with MS Fatigue Severity Scale scores. Bladder dysfunction is common in MS, and some patients manage their bladder dysfunction by limiting fluid intake, which could explain the dehydration in some cases.