Translate the available knowledge on ageing and dehydration into main messages for clinical practice. Older people are more susceptible to dehydration than younger people. This is partly due to lack of thirst sensation and changes in the water and sodium balance that naturally occur as people age. It is also, to some degree, attributable to the fact that elderly people, both those living at home and those living in institutions, often have various impairments, disabilities and/or handicaps (comorbidity). They also tend to use numerous drugs and medication for these illnesses (polypharmacy). Multimorbidity and polypharmacy often overstress the normal age-related physiological changes in the water and sodium balance and therefore increase elderly people's risk of dehydration,especially during intercurrent infections or warm weather. Elderly people, whether they are living on their own or in an institution, and especially elderly people that can no longer take care of themselves because of cognitive, sensory, motor and/or ADL impairments, need extra help to stay hydrated. The most important strategy is simply a matter of ensuring that elderly people consume a sufficient amount of fluids (at least 1.7 liters every 24 hours). Additional strategies include making healthy drinks and water easily available and accessible at all times and reminding and encouraging the elderly to consume these fluids. Elderly people should not be encouraged to consume large amounts of fluids at once but rather small amounts throughout the day. When the recommended fluid intake cannot, for whatever reason, be realized, fluids can be administered via catheter or by hypodermoclysis. In more specific and severe cases, fluids can be administered intravenously. The prevention, signaling and treatment of dehydration in the elderly is an important multidisciplinary endeavor. Formal and informal care providers need to continuously be aware of the risk factors and signs of dehydration in the elderly, especially during periods of very warm weather and when older people are ill. Standard professional care for high risk patients is imperative.