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Your Guide to Sexuality.
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A.

You were probably having a hard time finding the answer because there isn’t a simple one. As with almost all sex questions, we have to break this down a bit.

First off, we have to consider what you mean by “cum”. Do you mean you want to know when a guy is going to ejaculate, or specifically when to expect ejaculate to come into the picture (so to speak)? Or are you talking about how to tell if and when a guy is going to have an orgasm?

There is still a lot of misinformation out there about male sexual response, in particular people are sometimes confused to find out that ejaculation and orgasm in men are actually two separate events. Ejaculation is a physiological event, something you can usually observe, whereas orgasm is a perceived experience, which may or may not be something you can “see”.

Researchers have actually broken ejaculation down even further, describing it as three different events: emission, ejaculation, and orgasm. In the first stage, what they call emission, there are some muscular contractions and the semen is pushed to the base of the urethra (the tube that both urine and ejaculate come out of at the tip of the penis). In the second stage, ejaculation, the semen is propelled out of the penis. The third stage, orgasm, is far less understood, and refers to a subjective experience that may or may not accompany the ejaculation.

But back to your question, how best to tell when a man’s going to come. The easiest way to tell is to ask the man you’re having sex with to tell you, and ask for a bit of warning. Sometimes people feel embarrassed about this, or shy, or think that talking about what’s happening during sex takes the mystery out of it. In fact one of the best ways to incorporate more sexual communication in your life is to start by doing precisely what you’re asking about; have sex and describe to each other everything that’s happening. There’s nothing wrong with asking a guy to tell you when he’s going to come, and if you’re experiencing any anxiety about it then you should definitely ask.

What happens if a guy doesn’t know when he’s going to come? This is definitely a possibility, particularly with younger guys. There are some signs of impending ejaculation, although every guy is different and they won’t always apply. Some of the signs include:

• A feeling just prior to ejaculation that some guys describe as “tickling” and others say is just the feeling that they’ve gone over the top and can’t go back (researchers call this “ejaculatory inevitability”)
• Pre-ejaculate, also called pre-cum
• The testicles and scrotum rises up nearer to the body
• Sudden tension in the body just moments before ejaculation
• Change in breathing

Some of these you might be able to notice, others you’ll never catch, and still others won’t apply to some men who they don’t happen to. Of course the more you have sex with someone the better you can become at “reading” their body. You may notice other signs, like a particular spot where they get extra sweaty, or a way their body moves, or their breathing, or maybe they start to hum just before ejaculation. If you’re perceptive you can probably figure out the signs.

But the easier way to do this, and the one that works right away, is just to ask.

Sources:
Donatucci, C.F. “Etiology of Ejaculation and Pathophysiology of Premature Ejaculation” Journal of Sexual Medicine. Volume 3, Issue s4 (September 2006):303–308.