Dark purple urine: what should you know?

First check the urine in natural light and in a clean, clear container, because coloured toilet water or lighting can mislead. Purple or very dark urine may result from a mixture of red and blue pigments, food or medicines, or a sample that has changed while standing. In people using a urine bag, bacteria and chemical changes can produce a purple appearance; this needs clinical advice rather than home treatment. Dark urine with fever, burning, confusion, side pain, or yellow eyes may have a different cause.

Take a clear photograph only if it helps show the change, then contact a clinician or pharmacist for advice. Drink normally if you have no fluid restriction, but do not rely on water to correct a colour that remains unusual. Do not flush away a sample if a clinician has asked you to provide one, and do not start leftover antibiotics. List recent medicines, supplements, foods, urinary devices, and symptoms.

Get urgent help for confusion, collapse, severe weakness, inability to pass urine, severe back or side pain, fever with shaking, or repeated vomiting. Seek prompt assessment for yellow skin or eyes, visible blood, pain when passing urine, or purple urine that persists after checking the container and lighting. People with urinary catheters should contact their care team promptly about a new colour change.

Ask whether you need a fresh urine sample, whether a medicine or urinary device could explain the appearance, and which changes should trigger urgent care.