Summary Subcutaneous hydration, or hypodermoclysis (HDC), is a very simple technique that should be practised more often by doctors and nurses who care for older patients. It involves less discomfort, generates less cost and has fewer adverse effects than the intravenous route and may reduce the need for admission to the emergency department. The main indication is the management of mild to moderate dehydration, and prevention of dehydration in patients who are intolerant of oral intake. It should not be administered in situations of severe dehydration, in emergency situations, or in patients with fluid overload. Isotonic or hypotonic solutions must be used with appropriate electrolytes. Certain medicines can be given simultaneously by HDC and this may be especially valuable in palliative care settings. In most cases there is no need to add hyaluronidase.