Is it harmful to hold back your urine?

Holding back urine occasionally is not dangerous. However, holding it back for a longer period of time can be harmful to your body, as bacteria can enter your urinary tract and cause infections. 

Moreover, there is a risk that the bladder can lose strength, which can make urinating difficult. In addition, the high pressure from holding your urine can also risk damaging your kidneys. 

These are worst-case scenarios though, and are only risk factors if you hold back your urine on a regular basis.