Dark urine when fasting: what should you know?

When you drink less, your kidneys conserve water and make urine more concentrated. This can make urine look deep yellow or amber, especially after several hours without fluids. Heat, sweating, vomiting or diarrhoea can intensify fluid loss; dehydration is a common explanation.

Colour alone cannot identify the cause. Tea-coloured or brown urine, pale stools, yellowing of the eyes, itching, abdominal pain or unusual tiredness can point to a liver or bile problem and should not be dismissed as a fasting effect. A clinician may review your history and request a urine test or blood tests.

If your fasting plan allows fluids, drink regularly during permitted hours and notice whether the urine becomes lighter. Replace fluids gradually after sweating or illness, and avoid using someone else’s medication or supplements to change urine colour.

Keep a note of when the colour appears, how long it lasts, and whether you have pain, burning, fever or reduced urination. If fasting is part of a religious or dietary routine, ask a healthcare professional how to maintain hydration safely around it.

Arrange prompt medical advice if dark urine continues after normal drinking, returns repeatedly, or comes with yellow skin or eyes, very little urine, dizziness, fainting, fever, or pain in the side or abdomen. Seek urgent help for confusion, severe weakness, or inability to keep fluids down.

Ask whether your fasting routine, fluid intake, medicines or supplements could explain the colour; whether you need urine or blood testing; and which symptoms should make you stop fasting and seek care.