What should you know about dark urine after antibiotics?

The infection being treated may have reduced your fluid intake or caused fever, vomiting, or diarrhoea, making urine concentrated. Some medicines can change urine colour, but the exact drug matters, so keep the package or prescription available. Dark urine may also be unrelated to the antibiotic, including blood in the urinary tract or a liver reaction. Symptoms such as yellow eyes, itching, pale stools, rash, facial swelling, wheezing, severe diarrhoea, or worsening infection are more informative than colour alone. Antibiotics used for conditions such as acute bronchitis, cellulitis, or other infections should be reviewed in context.

Read the medicine instructions and do not stop, restart, or share an antibiotic without advice from the prescriber. Drink normally unless a clinician has limited your fluids, and replace losses from vomiting or diarrhoea gradually. Note the first dose, the colour change, other medicines, and any new symptoms. Contact the prescribing clinic or pharmacist soon if the urine remains dark, the colour is brown, or you feel worse. They may decide that urine or blood testing is needed.

Seek emergency help for trouble breathing, facial or throat swelling, collapse, confusion, severe weakness, or inability to pass urine. Obtain prompt medical care for yellowing, severe abdominal pain, fever with worsening illness, visible blood, severe diarrhoea, blistering rash, or urine that becomes cola-coloured.

Ask whether your specific antibiotic is known to alter urine colour, whether the treatment should change, and which tests can distinguish dehydration, bleeding, kidney irritation, or a liver reaction.