Dark yellow urine: what a test result may mean

Urine becomes deeper yellow when it contains less water, such as after sweating, vomiting, diarrhoea, or simply drinking less. B-complex vitamins and some medicines can also alter colour. Colour viewed in a toilet or collection cup may be affected by lighting, cleaning products, or the container.

Dark yellow colour alone does not diagnose dehydration or infection. Dry mouth, thirst, dizziness, reduced urination, or weakness make fluid loss more concerning. Burning, urgency, fever, or pain may point to a urinary problem and should be interpreted with the urine findings.

If you feel well, drink fluids regularly and observe whether the colour becomes lighter. Replace fluid lost through heat or illness with small, frequent drinks, unless a clinician has given you a fluid restriction. Keep a list of supplements and medicines to share at the appointment.

If dark urine persists, becomes brown or red, or appears with symptoms, arrange a clinical review. A [Urine Test](/treatments/diagnostics-and-screening/urine-test/) can check findings that colour cannot show.

Seek urgent help for confusion, fainting, severe weakness, inability to keep fluids down, or very little urine after fluid loss. These can signal serious dehydration or another acute problem; do not wait for the colour to change.

Arrange prompt assessment for fever with back or side pain, painful urination, visible blood, yellowing of the skin or eyes, or persistent dark urine. Urinary symptoms can occur with [Urinary Tract Infection](/conditions/urinary-tract-infection/) or [Kidney Infection](/conditions/kidney-infection/).

Could my medicines or supplements explain the colour? Do my symptoms suggest fluid loss or infection? Do I need a urine test or blood tests? How much fluid is appropriate if I have another medical condition?