What should you know about dehydration symptoms?

Mild dehydration may first feel like thirst, sticky saliva, dry lips, tiredness or a headache. As fluid loss continues, dizziness on standing, muscle cramps, weakness and reduced urine can appear. Dark urine can be a clue, but colour alone cannot diagnose dehydration because foods, medicines and other conditions can alter it.

Confusion, fainting, marked drowsiness, fast breathing or very little urine suggest a serious problem. Vomiting, diarrhoea, fever, heat exposure and heavy exercise can all cause fluid loss. Cloudy urine, painful urination or flank pain may point to another issue and should not be dismissed as dehydration.

Move to a cool place, rest and take frequent small sips of water. If vomiting or diarrhoea is present, an oral rehydration solution can replace water and salts when used exactly as directed. Avoid alcohol and pause strenuous activity. Check whether you are able to drink and whether urine output improves.

Do not force large amounts quickly if you feel nauseated. If symptoms do not settle, or the cause is unclear, contact a clinician. Explore [Dehydration](/conditions/dehydration/) for more context.

Seek urgent help for confusion, fainting, severe drowsiness, inability to keep fluids down or very little or no urine. Arrange prompt assessment for worsening dizziness, persistent vomiting or diarrhoea, severe weakness, chest symptoms or significant heat exposure. Get advice early for a baby, older adult or person with a chronic condition.

Tell the clinician when symptoms began, what fluid may have been lost, how often you are urinating and whether fever, pain, vomiting or diarrhoea is present. Ask whether testing or a specific rehydration plan is needed.