Side effects of dehydration

When the body loses more fluid than it replaces, blood volume and moisture available to tissues fall. You may pass urine less often, and urine may look darker or smell stronger. Reduced fluid in the bowel can contribute to constipation. Dry mouth, weakness, a fast heartbeat or light-headedness on standing can also occur. Dehydration may follow sweating, vomiting, diarrhoea, fever or difficulty drinking. Dark urine alone does not identify the cause; cloudy urine, burning or pain may point to another problem such as a urinary infection.

Move to a cool place if heat or exercise contributed, and take frequent small sips of water. An oral rehydration drink can help replace fluid and salts after substantial vomiting or diarrhoea. Continue gentle foods as tolerated and avoid alcohol while recovering. If you have heart or kidney disease, are pregnant, or take medicines that affect fluid balance, ask a clinician how much to drink. Treat the trigger as well: gastroenteritis and heat exhaustion may need assessment if symptoms persist.

Get urgent medical help for confusion, fainting, inability to keep fluids down, very little or no urine, severe weakness, breathing difficulty or a rapid worsening condition. Seek prompt advice if dizziness continues despite drinking, or if vomiting, diarrhoea or fever prevents rehydration. Severe side or back pain with dark urine also needs assessment because kidney stones or another urinary problem may be involved.

Ask what may have caused the fluid loss, whether your medicines need adjustment, and which drink is suitable for your situation. Mention urine changes, bowel symptoms, recent heat exposure, vomiting or diarrhoea, and how often you are passing urine.