Dark pee and antibiotics: what should you know?

Fever, sweating, vomiting, or diarrhoea can make urine concentrated. Some medicines change urine colour, while a new rash, swelling, wheeze, or marked weakness may indicate a reaction. Dark urine with yellow eyes, pale stools, nausea, or upper abdominal discomfort needs assessment for a liver problem. Burning, urgency, pelvic pain, or fever may indicate a urinary issue that is not covered by the prescribed antibiotic. The colour alone cannot show whether treatment is working.

Check the medicine name, dose, and start date, and read its patient instructions. Drink fluids normally unless a clinician has restricted them. Contact the prescriber or pharmacist before stopping a prescribed course, changing the dose, or taking someone else’s antibiotic. Keep a list of every medicine and supplement, including non-prescription products, because combinations can matter. A urine or blood test may be needed.

Seek emergency help for trouble breathing, facial swelling, collapse, severe blistering rash, confusion, or very little urine. Contact a clinician promptly for yellowing, severe abdominal or back pain, persistent vomiting, fever that is worsening, or dark urine that does not improve. If symptoms began soon after a new medicine, mention that timing clearly.

Ask whether the antibiotic can alter urine colour, whether your symptoms suggest a reaction or another infection, and exactly what to do about the next dose.