What dark urine can mean

Urine becomes darker when it is more concentrated, such as after sweating, vomiting, diarrhoea or not drinking enough. Dehydration may also cause thirst, a dry mouth, headache or passing urine less often. Heat exhaustion can produce similar fluid loss, especially after time in a hot environment.

Brown or cola-coloured urine can sometimes reflect bile pigments from a liver problem, including hepatitis. Blood, muscle breakdown and some medicines or foods can also alter colour. Colour alone cannot identify the cause, so note whether the change is amber, orange, brown, red or cloudy and whether it persists.

If you otherwise feel well and the urine became darker after heat, exercise or poor fluid intake, drink fluids gradually and monitor the next few times you pass urine. Replace fluids lost through vomiting or diarrhoea with advice from a pharmacist or clinician. Do not force large amounts quickly.

Review any new medicines, supplements or strongly coloured foods, and take a photo in good light if the change is difficult to describe. Arrange a clinician review if the colour does not return toward your usual pattern or keeps recurring.

Seek prompt medical advice for dark urine with yellow eyes or skin, pale stools, severe abdominal pain, fever, vomiting, confusion, marked weakness, or pain in the side or back. Get urgent help if you are unable to keep fluids down, are barely passing urine, or the urine is red with clots.

Ask whether you need urine and blood tests, whether a medicine or supplement could explain the colour, and which symptoms would make the situation urgent. Tell the clinician about recent heat exposure, exercise, illness, travel and changes in bowel movements.