Dark urine after flu: what to know

Fever and sweating can reduce body water, while a blocked nose, sore throat, nausea or fatigue may make drinking less appealing. Urine then becomes more concentrated. Dark urine can also follow medicines, supplements or another illness occurring during recovery. Brown urine with yellow eyes, pale stools or itching raises concern for a liver-related problem. Muscle pain and cola-coloured urine after a viral illness need prompt review because muscle pigment can strain the kidneys.

Take frequent, comfortable drinks and monitor whether you are urinating as usual. Rest, follow the medicine label, and avoid adding supplements without checking their ingredients. Record the urine colour, fever pattern, medicines and any vomiting or diarrhoea. If your urine remains dark after you are eating and drinking normally, contact a clinician. They may use urine and blood tests to look for concentration, infection, blood, liver changes or kidney stress.

Seek urgent care for confusion, fainting, breathing difficulty, very little urine, repeated vomiting, severe weakness, severe abdominal pain, or yellowing of the skin or eyes. Cola-coloured urine with significant muscle pain also warrants urgent assessment. Contact a clinician promptly if dark urine persists, becomes red or brown, or occurs with burning, fever or flank pain.

Ask whether dehydration explains the colour, whether any flu medicine could contribute, and whether urine, kidney or liver tests are needed. Ask how to manage fluids if you have another medical condition.