Why is urine yellow
Urine, much like feces, acts as a waste disposal system for our body. Containing a number of different chemicals such as ammonia (broken down into urea by our kidneys), sugar, water and urobilins, normal urine is a pale yellow color and should be passed by our body on a regular basis.
Urobilins contained within urine are the broken-down products of bilirubin, the coloring that creates a yellowish tint in bruises, bile and feces as it is itself a byproduct of broken-down old blood cells. Most of the bilirubin contained within our bodies is processed by the liver or, more specifically, the gall bladder and passed on to our intestinal tract for processing. Unfortunately this cannot always clean out all bilirubin necessary from our system and as such the kidneys work to filter out whatever amount is remaining and pass it to the bladder for storage and disposal.
The reason for the color intensity of urine lies in the amount of bilirubin contained within the urine itself. When dehydrated your kidkeys and other fluid disposal systems operate at a much slower pace, thus allow bilirubin to build-up within your body and give urine a darker yellow color. Regular hydration, on the other hand, causes our body to process liquids more quickly and flush out the bilirubin on a more regular basis, hence giving urine a clearer color.
Should your urine not be yellow this may indicate a problem somewhere along your bilirubin processing or urinary tract lines and should generally be examined by a doctor as soon as possible. Red or brown in the urine, for example, may indicate a bleed somewhere in either your kidneys, bladder or transfer tubes and could be a sign of a serious problem such as kidney stones.
Other colors, however, may not be so worrying as they may simply be the result of your diet at the time. Regularly consuming carrots, for instance, will generally turn your urine a more orange color due to the various vitamins and chemicals contained within them, while some vitamins or other medications are also known to turn urine various colors depending on what particular type you have been consuming at that time.