What should you know about physical signs of dehydration?

Dehydration happens when the body loses more fluid than it replaces. It may follow vomiting, diarrhoea, fever, heavy sweating, hot weather, or difficulty drinking. Children, older adults and people with some medical conditions can become unwell more quickly.

Urine may become darker and less frequent, while the mouth, lips and tongue feel dry. Headache, weakness, light-headedness, muscle cramps and a fast heartbeat can occur as fluid loss becomes more significant. Dark urine can have other causes, and cloudy urine may relate to infection or another urinary problem, so one sign should not be interpreted alone.

Sip fluids regularly. If vomiting or diarrhoea is present, an oral rehydration solution may replace water and salts more appropriately than relying on plain water alone. Take small sips and increase gradually if your stomach allows. Continue suitable food when able, and rest somewhere cool after heat or exertion.

Ask a pharmacist or clinician what is suitable if you have kidney, heart or liver disease, are pregnant, or have been told to restrict fluids. Do not use someone else’s prescribed treatment. Monitor alertness, urine output and the ability to drink.

Seek urgent care for confusion, fainting, severe weakness, difficulty staying awake, very little or no urine, a rapid worsening after heat exposure, or inability to keep fluids down. Blood in vomit or stool, severe abdominal pain, or symptoms of a urinary infection also need prompt assessment. Dehydration with kidney-stone pain can require medical attention.

Ask how much and what type of fluid is appropriate, whether medicines may be increasing fluid loss, and how to manage dehydration during gastroenteritis or hot weather. Mention diabetes, kidney problems, pregnancy, recent travel, and every symptom that accompanied the fluid loss.