When was the last time you examined the color of your urine? In our experiences as physicians, we are often surprised by how much people can tell us about how their pee looks. If you listen to the “experts,” you probably think that your urine should be pale yellow or almost clear, and if your urine is darker than that, you should be concerned about being dehydrated. If you have yellow pee, you must need more water—think about the six to eight glasses of water a day. Right?
This is really just a half-truth. It is true that your urine gets darker when there is less of it. When your body needs to keep in more fluids (such as when you are dehydrated), you will pee less (a smaller volume of urine), and that urine will be darker. But having yellow urine does not mean that you are dehydrated! The color of the urine depends on its osmolality, which is the technical term for how much stuff is dissolved in the liquid. When there is more stuff dissolved in a given volume of urine, the urine is more concentrated, and therefore it looks darker. However, the osmolality of normal urine can be very different from person to person. One specialist in fluid regulation tested the urine of sixty-nine healthy young adults and measured the average volume and concentration of their urine. For this group, all of whom were considered well hydrated and healthy, the average volume of urine was 1.5 liters per day and the average concentration was 600 mosmol/kg H2O. At this average concentration, urine is moderately yellow in color, which could be interpreted as “dark” compared to the recommended “clear” or “pale yellow” you may think of as your goal. This concentration is, in fact, well within the normal range. Most of the time, normal urine from a healthy, well-hydrated person may be very yellow. If you are struggling to get it clear or pale yellow, you are probably worrying for nothing.
There is one caveat to dismissing this pee-color business. Sometimes, doctors will suggest that people with medical conditions such as repeated kidney stones make an extra effort to dilute their urine. If a doctor has recommended that you try to get your urine lighter than normal because of a medical condition, then you should listen to their health guidance on this particular issue. For those of you who are perfectly healthy, don’t worry if your urine is yellow! If you are thirsty, drink. If you are not, don’t worry about it!