What should you know about clinical dehydration?

Fluid loss can follow vomiting, diarrhoea, fever, sweating, heat exposure, or difficulty drinking. Early signs may include thirst, dry mouth, headache, tiredness, dizziness, constipation, and dark urine. Severe dehydration can reduce blood flow and affect alertness, heart rate, and kidney function. Dark urine can have other causes, so urine colour alone cannot confirm dehydration; the wider history and examination matter.

Sip fluids regularly rather than waiting for intense thirst. After vomiting or diarrhoea, an oral rehydration solution can replace water and salts; follow the packet instructions and use a prepared solution as directed. Continue suitable food when you can. Infants, older adults, pregnant people, and anyone with kidney, heart, or fluid-balance problems may need tailored advice. Do not force large amounts quickly if vomiting continues.

Get urgent help for confusion, fainting, severe weakness, very little or no urine, inability to keep fluids down, rapid breathing, or signs of heat illness. Seek prompt care when diarrhoea or vomiting continues, urine becomes markedly reduced, or dehydration occurs with severe abdominal pain, fever, or blood. A clinician may need to give monitored fluids and investigate the cause.

Ask how much fluid is appropriate for your health conditions, whether an oral rehydration solution is suitable, and what signs mean you need urgent review. Mention recent heat exposure, vomiting, diarrhoea, urinary symptoms, medicines, and any history of kidney stones or urinary infection.