Dark urine and kidney disease: what to know

Kidney problems may cause blood in urine, foamy urine, changes in how often you urinate, swelling around the ankles or eyes, or pain in the side or back. Dark urine after sweating or low fluid intake is often concentration rather than kidney damage. Brown or cola-coloured urine can also occur when blood or muscle pigments are present. Some kidney conditions cause few obvious symptoms, so colour alone is not a reliable guide. A urine test can look for blood, protein, and infection, while blood tests can assess kidney filtering.

Note the colour, timing, fluid intake, exercise, pain, swelling, and any change in urination. Bring a list of medicines and supplements, including non-prescription pain relievers. Drink normally unless you have been told to restrict fluids; forcing large amounts is not a treatment for an unknown cause. Arrange a medical review if the change persists, recurs, or comes with foam, blood, swelling, or pain. Testing may include a clean urine sample, blood pressure measurement, and blood tests.

Seek urgent care for severe flank pain, fever with urinary symptoms, inability to urinate, very little urine, visible heavy bleeding, marked swelling, breathlessness, confusion, or fainting. Prompt assessment is also sensible when dark urine appears after strenuous activity with muscle pain or weakness. People with known kidney disease should use their clinician's safety plan when urine output or colour changes.

Could the colour be from blood, protein, dehydration, or a medicine? Which urine and kidney blood tests do I need? Should I change any pain medicines? What urine-output or swelling changes should trigger urgent care?