Normal urine is clear and has colour ranging from light to dark yellow. The first morning urine is typically dark because it is concentrated and one hasn’t drunk water overnight. On the other hand if a lot of water is consumed the urine is dilute and light yellow coloured. Some foods and additives can change the colour of urine. Beetroot and carrot can lend their colour to the urine when consumed in large quantities. Artificial food dyes can colour the urine if junk food is consumed. Certain commonly used medications can change urine colour. The best known is vitamin B complex supplements which can turn the urine orange. Rifampicin (used for tuberculosis) and phenytoin(used for seizures) can turn the urine reddish. Sometimes it is obvious that blood is being passed in the urine and urine turns red. A urine examination reveals presence of red blood cells (RBC’s) or blood molecules (” hemoglobin”) in the blood. The causes of blood in urine are many and needs evaluation by a kidney specialist. It could be something innocuous like a minor urinary bladder infection or something serious like a cancer of the urinary tract. Sometimes blood in urine could be a sign of destruction of blood cells within the blood vessels leading to low hemoglobin(“hemolytic anemia”). This obviously needs a very detailed evaluation by a specialist. Very intense exercise, especially in people unaccustomed to it, can lead to destruction of muscle fibres. Muscle protein, called “myoglobin” , can then be excreted in the urine giving it a pinkish colour. When lymph leakage occurs in the urine, it gives it a milky white appearance. An unusual green coloured urine can be seen when there is urinary tract infection by a type of bacteria called pseudomonas. Some infections can turn the urine purple too! The anti-depressant drug “amitriptyline’ can also lend a greenish hue to the urine. In some rare diseases, the urine colour can help in diagnosis — examples being alkaptonuria(black urine), melanoma (black), red (porphyria). One important aspect to know well is that urine colour rarely helps in diagnosis by itself. It only helps to guide further investigation and management. Deviations from its usual yellow colour (light to dark) don’t give very useful information as far as the person’s health is concerned.Dr. Prashant C Dheerendra, Senior Consultant Kidney Specialist, Apollo hospitals, Bannerghatta Road, Bangalore.