Occasional, short-term holding of urine is not harmful to the human body, but long-term, regular holding of urine is very harmful to the human body. About 100-150ml of urine in the bladder can produce the urge to urinate, if the environmental conditions allow, the body can go to active urination. If you hold your urine for a long time and do not take the initiative to urinate, it will cause the sensitivity of the bladder to decrease over time, i.e., about 200ml or more of urine in the bladder, or even more urine to produce the urge to urinate. In the long run, the urine stored in the bladder will easily harbor bacteria, which will cause the occurrence of urinary tract infections, such as acute cystitis and acute pyelonephritis. If you often hold back urine, a large amount of urine in the bladder can dilate the bladder, causing bladder muscle fibers to degenerate, the bladder can be formed in the bladder trabeculae small rooms, will gradually weaken the bladder muscle contraction force, resulting in urinary difficulties, and in severe cases, will lead to urinary retention. Prolonged urinary retention can also cause hydronephrosis, leading to renal insufficiency.