Dark urine and dry mouth: what they can mean

Fluid loss can happen after sweating, vomiting, diarrhoea, fever, exercise, or simply drinking less than usual. Urine may become more noticeable in the morning or after time in a hot environment. The shade alone cannot identify the cause.

When the body has less available fluid, the kidneys conserve water and produce more concentrated urine. This can make urine look darker and the mouth feel sticky or dry. Thirst, headache, tiredness, dizziness, and passing urine less often can occur alongside fluid loss. Dehydration is a possible explanation, not a diagnosis based on these symptoms alone.

Dark brown urine, tea-coloured urine, red urine, cloudy urine, a strong unusual smell, burning, or pain can point to a different problem. Yellowing of the skin or eyes, pale stools, nausea, or pain under the ribs should also be checked because liver or bile-duct conditions can change urine colour. Some medicines, supplements, and foods can alter urine appearance.

If you are alert and able to drink, take frequent small sips of water and continue with normal meals. After heavy sweating or gastrointestinal illness, an oral rehydration solution may help replace lost salts; follow the product directions. Rest somewhere cool if heat or exertion may have contributed.

Notice whether your urine becomes lighter and whether your mouth feels less dry as you replace fluids. Do not force large amounts quickly, and ask a clinician about fluid advice if you have kidney, heart, or liver disease, or have been told to restrict drinks. Avoid alcohol while you are recovering from fluid loss.

Seek urgent medical help if you are confused, faint, very drowsy, unable to keep fluids down, breathing unusually fast, or passing very little or no urine. These signs can indicate severe fluid loss or another urgent illness.

Arrange prompt medical advice for dark urine that does not improve after drinking, blood in the urine, severe pain, fever, painful urination, yellow skin or eyes, or repeated vomiting or diarrhoea. A clinician may review your medicines, examine you, and test urine or blood to find the cause.

You could ask: Could a medicine or supplement be changing my urine colour? Do my symptoms suggest fluid loss or another cause? Should I have urine or blood tests? What should I drink if I have another condition that affects fluid balance?