What should you know about extreme dehydration symptoms?

Fluid loss may first cause thirst, dry lips or mouth, headache, tiredness, darker urine, and less frequent urination. More advanced symptoms include dizziness when standing, muscle cramps, a fast heartbeat, unusual weakness, irritability, or difficulty concentrating. Confusion, fainting, very little urine, rapid breathing, or inability to drink are severe warning signs. Vomiting and diarrhoea can cause dehydration quickly, as can prolonged heat exposure. Cloudy urine, painful urination, fever, or pain in the side may suggest a urinary tract or kidney condition and should not be explained away as dehydration without assessment.

Stop strenuous activity and move to a cool or shaded place. If the person is alert and can swallow, offer small, frequent sips of water or an oral rehydration drink. With ongoing diarrhoea or vomiting, a pharmacist or clinician can advise on rehydration products. Keep track of urine, alertness, and whether fluids stay down. Do not force drinks into a person who is drowsy, confused, faint, or having trouble swallowing; place them safely and call emergency services. People with fluid restrictions need advice tailored to their condition.

Call for emergency help if confusion, collapse, fainting, severe drowsiness, very little or no urine, rapid breathing, chest pain, or inability to keep fluids down occurs. After heat exposure, altered behaviour or worsening weakness is urgent. Seek prompt medical review for dehydration with severe abdominal pain, blood in vomit or stool, high fever, flank pain, or symptoms that do not improve with drinking. Young children, older adults, and people with chronic illness may need assessment sooner.

Ask which symptoms indicate emergency care, how to replace fluids safely, whether an oral rehydration solution is appropriate, and how to monitor recovery. Tell the clinician about recent heat exposure, vomiting, diarrhoea, urine changes, medical conditions, and medicines that increase urine output.