Urine
Urine, as such, is commonly associated with waste, something completely worthless. There are numerous expressions reflecting this: In Switzerland, they say someone is urinating when speaking nonsense; in English, the phrase "piss something away" is used to describe wasting something; in Sweden, "piss on something" conveys dismissing or treating something with disdain. In this sense, urine is simply worthless waste.
Needing to urinate
Feeling an urgent need to urinate in a dream symbolizes something "pressing" that needs to come out or a "pressure" we feel. This may stem from external demands or an inner need to express genuine feelings or thoughts. (See also Toilet.)
"People often wander through nightmares with this need but never find the right place, which always means they are unable to express their true nature." (Katten i saga och verklighet, p. 148.)
Wetting oneself, or similar involuntary release, can symbolize an inability to contain something—whatever it represents in the given situation.
Genuine expression
Urinating generally symbolizes "expressing oneself genuinely" (Skuggan och det onda i sagor, p. 151). It reflects being authentically oneself. Individuals with a false persona, or in some way are not genuine, might experience inhibitions, for instance, regarding more or less public toilet visits.
At the same time, urination is an inescapable need. While one can skip meals, sleep, or other basic necessities for a time, one cannot avoid going to the toilet when the need arises. We are at the mercy of this bodily function. Thus, "urinating" can sometimes symbolize, "This is who I am, and that’s the whole truth"; in dreams, it is simply an expression of being oneself.
The function of emotions
Urinating is connected to the emotional function. Just as the heart is traditionally associated with emotions, so too are the kidneys. Holding back the need to urinate in dreams represents suppressing the need to express genuine emotions, often due to inhibitions.
Rain, water – aqua permanens
Urinating is mythologically and idiomatically associated with rain and water in cultures worldwide. This is reflected, for instance, in the French expression for heavy rain, where they say "the cow is urinating"; similarly, in Swedish, the phrase "throwing water" is used; lastly, "the boy's urine" was, for the alchemists, an allegory for aqua permanens.