Provision of appropriate nutrition and hydration is a hallmark of compassionate care but is often neglected in all types of healthcare.1 2 3 4 5 These problems are not new and have been reported in the medical literature for nearly four decades.6 7 The consequences are clinically and financially costly. The estimated excess UK health related costs of malnutrition are at least £13bn (€15bn; $20bn) annually.1Patients with malnutrition have a deficit of energy, protein, vitamins, or minerals, and this has measurable adverse effects on the body.2 Those at risk include patients with poor intake or appetite, dysphagia, chronic disease, or poor functional and social or cognitive ability. Defining adequate hydration is complex. It is estimated by the synthesis of clinical indicators (such as confusion, tachycardia, blood pressure, and thirst), serum biochemistry (such as urea and creatinine), tissue perfusion markers (such as urine output, lactate levels), and urine specific gravity. We examine the scale of malnutrition and poor hydration in our hospitals and communities, explain why it matters, and put forward proposals for change.