Dark urine when sick: what should you know?

Fever, sweating, vomiting and diarrhoea remove fluid, while nausea, sore throat or fatigue may make drinking harder. The kidneys then conserve water, producing smaller amounts of more concentrated urine. Dehydration can also cause thirst, dry mouth, headache and dizziness.

Not every dark colour comes from fluid loss. Some infections affect the liver or bile system, and some medicines or supplements change urine shade. Brown urine, yellow eyes, pale stools, itching, abdominal pain or unusual sleepiness should be assessed rather than attributed to the illness alone.

Take frequent small sips if nausea makes a full glass difficult. If vomiting or diarrhoea continues, ask a pharmacist or clinician about a suitable rehydration plan. Track urination, temperature, fluid intake and any new medicines so you can describe the pattern clearly.

Rest and follow the treatment instructions for the illness. Do not take leftover antibiotics or stop prescribed treatment without advice. People with kidney, heart or liver conditions, older adults and children may need tailored guidance when losing fluids.

Get prompt medical advice for dark urine that does not improve as you recover, repeated vomiting, ongoing diarrhoea, very little urine, severe dizziness, fever with flank pain, or yellowing of the skin or eyes. Seek urgent help for confusion, fainting, severe weakness or inability to keep fluids down.

Ask which fluids are suitable, whether your illness or medicines can affect urine colour, how to monitor dehydration, and whether you need urine, kidney or liver testing.