Elderly living in nursing homes and long-term care units are well-known to be vulnerable to dehydration. Insufficient water intake contributes to suboptimal hydration status and leads to decreased quality of life and global health status. Based on published studies, 32 to 96% of nursing home residents had insufficient water intake and more than 50% drank less than 1.5L per day. Risk factors contributing to decreased water intake in nursing home residents can be divided into two categories, depending whether they apply to the individuals per se (individual factors) or their social and institutional environment (environmental factors). Water intake is associated with meals and medication administration frequency. Diminished thirst sensation, intentional fluid restriction, dysphagia and functional dependency are individual factors recognized as most contributing to decreased water intake. Lack of familial support and insufficient staff are also important since they can contribute to decreased patients' assistance. Dietitians can play a fundamental role in preventing suboptimal hydration status by identifying risk factors that are known to compromise individual's water intake and by implementing corrective measures.