Urine is a body fluid which consists of a high content of water and multiple metabolic waste products; especially nitrogenous compounds such as urea, creatinine and other metabolic waste components. They are filtered from the blood using the kidneys. Urine is stored in the urinary bladder and is excreted from the body through the urethra. Moreover, there are several substances which may be excreted in urine due to an injury or infection of the glomeruli of the kidneys, which can alter the ability of the nephron to reabsorb or filter the different components of blood plasma.

Urine analysis
Urinalysis is a useful disease diagnostic media. Urine was the first body fluid to be examined during disease diagnosis. Normally, in medical laboratories, urinalysis is done for the detection of overall health assessments (routine medical examination, pre-surgery preparation, or upon hospital admission to screen for the disorders including kidney and liver disease), Medical Diagnosis (symptoms including abdominal pain, back pain, frequent or painful urination and blood in urine), Infections detection, Medical Monitoring (diagnosis of kidney disease to track both condition and treatment) and Specific testing (pregnancy tests and drug screenings).

Types of urine examinations
Mainly urine analysis is divided into four main groups:
1.Physicochemical properties (Colour, Appearance, Volume, Specific gravity and Odor)
2. Chemical examination (pH, Sugar,  Ketone bodies , Protein, Nitrites, Bilirubine  and Urobilinogen)
3. Microscopic examination (white blood cells, red blood cells, epithelial cells, casts, crystals, bacteria, yeast and non bacterial organisms)
4. Bacterial screening (Gram staining and colony count)
Among the above mentioned properties of urine, colour takes prominent place. This is because the colour of urine has a specific ability to indicate the status of human health. 
Urine colour normally ranges between light yellow and dark amber. A colour change in urine is usually normal, but just occasionally it may be a sign of bad health. The colour of urine becomes darker due to high concentration. Because people normally sleep for several hours without having a drink their urine is normally darker when urinating first thing in the morning. Dark coloured urine during the day or evening may be a sign that someone is dehydrated; meaning he or she is not taking enough fluids. Drinking lots of fluids will make urine lighter.
Moreover, in some situations, eating certain foods, taking vitamin supplements and medications can affect the colour of urine. However, the intensity of changes to the colour of urine will depend on the amount of consumed food, supplements or medication. But in some situations, the colour change in urine  is an indication of a medical problem such as a urinary tract infection, kidney, bladder or liver problem etc. 
(The writer holds a MSc Degree in Industrial and Environmental Chemistry from the University of Kelaniya and a BSc in Food Production and a Technology Management degree from the Wayamba University of Sri Lanka)