Perfectly healthy urine is typically pale yellow in color.
The yellow comes from a byproduct known as urobilin, developed as part of the digestive process in the human body. Pale yellow indicates normal bodily function, along with a normal level of the body’s overall water content, or hydration. The yellow color of urine is influenced by the water content in the body at any given time. An overabundance of fluid in the body causes the yellow color to become pale, and a lack or shortage of fluids tends to make the yellow brighter or more vivid.
So if pale yellow colored urine is healthy and normal, what about bright or bold yellow urine? Bright yellow urine is a telltale sign of either not enough hydration present in the body, or an overabundance of vitamin B2 (riboflavin), either from foods or supplements. Either of these conditions, if only temporary, are harmless and of no real concern. If the bright yellow color is due to dehydration, simply consuming more fluids should make the pee less vivid in no time at all. If the bright yellow color is due to food or vitamin supplement pills containing large amounts of vitamin B2, the yellow color will lose its brightness just as soon as the body has finished processing and discarding the extra vitamin B2. The body can use and absorb only so much in the form of B vitamins, except for vitamins B12 and B9 (folate), which are stored in the liver.
Excess vitamins typically get discarded naturally either through feces or urine. Because B vitamins are water-soluble, excess amounts are normally excreted via the urine stream. Foods that are high in B vitamins include red meats, organ meats, poultry, fish, eggs, cheese, milk, whole grains, beans and lentils, almonds, sunflower seeds, asparagus, broccoli, kale, spinach, bananas, oranges, avocados and whole grain foods such as breads, cereals, pastas, brown rice and barley. But, unless consumed in exceptionally large quantities, none of these foods should turn your pee bright yellow.
Excess amounts of vitamin B2 or Riboflavin typically come from taking a vitamin supplement pill. So, the harmless, but guilty party accounting for temporary bright yellow pee color is almost always lack of proper hydration or the result of consuming supplement pills high in vitamin B2.
Please note that the effects of an overload of B vitamins on urine affect color only. If your pee smells bad, or is cloudy, or is significantly different from what you normally experience, it could be simple dehydration, but it could also be other, possibly more serious issues going on.