Dark yellow urine: what does it mean?

The kidneys make urine more concentrated when the body has less available fluid. A darker shade after a hot day, activity, illness, or a long period without drinking may improve as fluids are replaced. Urine colour can also change after some medicines, supplements, or foods. Heat exhaustion is a concern when fluid loss comes with dizziness, headache, nausea, weakness, or heavy sweating.

Colour alone cannot distinguish dehydration from liver inflammation, infection, or a urinary problem. Brown or tea-coloured urine, yellow eyes, pale stools, fever, pain, burning, or much less urine changes the picture and should not be dismissed as simple thirst.

If you are otherwise well, drink regularly according to thirst and usual medical advice, then see whether the colour lightens. Keep track of when it started and any heat exposure, vomiting, diarrhoea, new products, pain, or change in urine amount. Seek a GP assessment if it continues, returns without a clear trigger, or appears with other symptoms. Do not take antibiotics or stop regular treatment solely because of urine colour.

Use urgent services for fainting, confusion, severe weakness, severe pain, repeated vomiting, yellowing of skin or eyes, high fever, inability to keep fluids down, or inability to pass urine. A red, brown, or tea-coloured change also warrants prompt advice, especially if it is persistent.

You can ask whether the appearance suggests concentrated urine, whether testing is needed, how much to drink given your health history, and what exact changes should lead to urgent review.