Two common signs of dehydration

Dehydration happens when the body loses more fluid than it takes in. Fluid loss can follow sweating, vomiting, diarrhoea, fever, or simply not drinking enough. Thirst may be noticeable before other symptoms, while urine changes can offer another useful clue.

Thirst is the body’s request for more fluid. Dark yellow urine or passing urine less often can occur when the kidneys conserve water. These signs can appear together, but either one may have another explanation. Certain foods, medicines, sweating, and some illnesses can alter urine colour or thirst.

Dry mouth, tiredness, headache, dizziness, and muscle cramps may accompany dehydration. A person who is very young, older, pregnant, unwell, or unable to drink can become dehydrated more quickly. Dark urine is different from cloudy urine, which may have other causes.

Start taking small, frequent sips of water and continue as thirst settles. If vomiting or diarrhoea has caused fluid loss, an oral rehydration solution can help replace water and salts; follow the product instructions. Avoid relying on alcohol, and do not force large amounts quickly if you feel nauseated.

Rest somewhere cool if heat or heavy activity may have contributed. Keep track of whether you can drink and whether you are passing urine. If symptoms do not begin to improve, or if you have a medical condition that affects fluid balance, contact a clinician for tailored advice.

Seek urgent medical help if you are confused, unusually drowsy, faint, unable to keep fluids down, or barely passing urine. Get prompt advice for severe dizziness, a fast heartbeat, worsening weakness, blood in vomit or stool, or signs of serious illness such as severe abdominal pain or breathing difficulty.

Children, older adults, and people with diabetes, kidney disease, or heart problems may need earlier assessment because fluid replacement may require special care. Dehydration after prolonged heat exposure also warrants prompt attention, especially when sweating stops or the skin becomes hot.

You could ask: What might be causing my fluid loss? How much should I drink given my health conditions and medicines? Do I need an oral rehydration solution? Which changes in urine, alertness, or vomiting mean I should seek urgent care?