Does masturbation cause uti?

It shouldn't: Masturbation without rubbing the urethral meatus (the hole where the urine (pee) comes out) should not be related to uti's. That means one can have a UTI regardless of one's masturbation. Mutual masturbation is a little more risky because one person may not know where the other person's urethral meatus is. It may be wise to learn one's anatomy to avoid rubbing somebody wrong.

Unlikely but possibl: Male masturbation is highly unlikely to cause utis, bacteria would have to travel quite a distance to reach the bladder where they can multiply. In women there is a slight chance of UTI if masturbation includes friction on + around urethral meatus because urethra is very short. Depends also on presence of bacteria at the urethral opening. Risk for utis probably increases with vibrator masturbation.

UTI: Masturbation, if non-traumatic, will not cause uti. In women, however, if the masturbation is with a dildo or vibrator, there may be mild swelling of the urethra (tube from bladder to outside) and this can predispose to uti.