Does urinating kill sperm leftover in the urethra?

A study done in 1998 in-vitro showed that sperm motility (health) was reduced by urine ammonia. [1]

Beyond that, there is no clear evidence on whether urine is spermicidal, excepting the clearing through physical means of residual semen post-ejaculation.

I would assume that this is pertaining to whether it is safe for further sexual encounters post-urination as part of contraception. Barrier methods like condoms would still be advised to avoid unwanted pregnancies.

Do keep safe and protected!

Reference:

1. Kim, S. C., & Kim, H. W. (1998). Effects of nitrogenous components of urine on sperm motility: an in vitro study. International journal of andrology, 21(1), 29-33.

Pre-cum can contain sperm (especially by picking up sperm left behind in the urethra from a previous ejaculation), but if you urinate between sexual encounters, nearly all the remaining sperm in the urethra will be flushed out.

Interestingly enough, even though I couldn’t find any literature on whether urine kills sperm, one could assume that it does, extrapolating from the theory that pre-cum is alkaline to neutralize the acidic remnants of urine present in the urethra (in order to create a “safe passage” for your sperm). Hence, the converse must also be true – ie the acidity of your pee damages/kills sperm.

So if you’ve urinated several times between ejaculations, the likelihood is that your pre-cum will contain so little sperm that it wouldn’t present any pregnancy risk (which is what I presume you are asking about).

Having said that, about 73% of couples who use the “withdrawal method” become pregnant within 1 year. Something to bear in mind, if you want to avoid a pregnancy!

Cheers