What should you know about antibiotic dark urine?

Check the medicine leaflet for known colour changes and consider whether you have been drinking less or losing fluids through fever, vomiting, diarrhoea, or heavy sweating. The colour alone cannot identify the cause.

Certain antibiotics or their breakdown products can turn urine brown, orange, or red without causing injury. A clinician or pharmacist can confirm whether this is expected for your exact medicine. Concentrated urine from dehydration is often deep yellow or amber and may have a stronger smell.

Tea- or cola-coloured urine can also occur when bile pigments, blood, or muscle proteins enter the urine. Dark urine together with yellow eyes or skin, pale stools, itching, nausea, or upper abdominal discomfort may indicate a liver or bile-flow problem. Pink or red urine, clots, burning, flank pain, or fever may point to bleeding or a urinary problem and should not be assumed to be a medicine stain.

Note when the colour started, the antibiotic name and dose, other medicines or supplements, and any accompanying symptoms. Look at the urine in good light and check whether the change persists across several trips to the toilet. If you can drink normally and have no fluid restriction, take regular fluids and see whether concentrated urine becomes lighter.

Contact the prescriber or a pharmacist the same day if the colour is unexplained, persists despite adequate fluids, or began soon after a new medicine. Do not change the dose or stop the course solely because of colour without professional advice. A clinician may review the medication list and arrange urine, blood, liver, or kidney tests according to the symptoms.

Seek urgent medical assessment if dark urine occurs with yellow skin or eyes, pale stools, severe abdominal or flank pain, repeated vomiting, fever with feeling very unwell, swelling, confusion, marked weakness, visible blood or clots, or much less urine than usual. These features can signal a liver, kidney, urinary, or severe dehydration problem that needs examination.

Call emergency services for trouble breathing, swelling of the face or throat, fainting, or a widespread blistering or peeling rash. Take the antibiotic packet or a clear photo of its label so the care team can identify the medicine and dose quickly.

Ask whether urine discolouration is an expected effect of your specific antibiotic, whether any other medicine could contribute, and which symptoms would mean you should avoid the next dose while seeking urgent advice. Also ask whether your fluid intake is appropriate for your health and whether testing is needed if the colour does not clear.