Yellow urine is often normal and is commonly caused by the natural pigment urochrome. Darker yellow urine can occur when you are not drinking enough fluids and may indicate dehydration. Certain vitamins, supplements, foods, and medications can also make urine appear bright or dark yellow. If the yellow colour persists despite adequate hydration or is accompanied by symptoms such as pain or burning during urination, fever, blood in the urine, abdominal pain, or yellowing of the eyes or skin, consult a doctor for a proper evaluation to determine the underlying cause.