Effects of Dehydration: What You Should Know

The body loses water through sweating, urine, breathing, vomiting or diarrhoea. When intake does not replace that loss, thirst, a dry mouth, tiredness, headache and dizziness can develop. Urine may become darker and less frequent. Reduced fluid in the bowel can make stools harder, contributing to constipation.

More marked dehydration can lower blood pressure and make the heart beat faster. It can also reduce alertness and make it harder to concentrate. Hot conditions and heavy exertion increase fluid loss; gastroenteritis and heat exhaustion are common situations in which dehydration can develop.

Start taking frequent small sips of water. If vomiting or diarrhoea is present, an oral rehydration drink can replace water and salts more effectively than relying on plain water alone. Rest somewhere cool, loosen extra clothing and pause strenuous activity. Keep monitoring thirst, urine colour and how often you pass urine.

Seek advice about fluid replacement if you have kidney or heart disease, are pregnant, or take medicines that affect fluid balance. Avoid using very sugary drinks as your main rehydration choice.

Get urgent medical help for confusion, fainting, severe weakness, inability to keep fluids down, very little or no urine, or breathing that feels unusually rapid. Heat-related illness with a high temperature or altered behaviour also needs urgent assessment.

Arrange medical advice when symptoms are worsening, urine stays very dark despite drinking, or fluid loss from vomiting, diarrhoea or sweating continues. A clinician can look for the cause and assess whether you need supervised rehydration.

Could a medicine or illness be contributing to my fluid loss? Which rehydration drink is suitable for me? What symptoms should prompt urgent help?