13 Things You Need To Know About Semen

Photographed by Kate Anglestein.
There are almost as many things to know about semen as there are individual sperm inside of it.

Sure, we often talk about semen in the context of the reproductive process, but not everyone having sex is doing so with the goal of pregnancy. There's a whole world of semen beyond fertilization, and if you find yourself in frequent contact with it, you might have some questions. Where does it come from? What does it say about a person's health? Is it actually okay to swallow it?

To answer these questions, we spoke to Philip Werthman, MD, urologist and director of the Center for Male Reproductive Medicine and Vasectomy Reversal in Los Angeles, and Jen Caudle, DO, family physician and assistant professor at Rowan University School of Osteopathic Medicine in Stratford, NJ. They helped break down all of the important facts about semen (like what exactly it even is), as well as dispel some common myths.

Ahead, 13 facts you need to know about semen.


The gap between what we learned in sex ed and what we're learning through sexual experience is big — way too big. So we're helping to connect those dots by talking about the realities of sex, from how it's done to how to make sure it's consensual, safe, healthy, and pleasurable all at once. Check out more, here.

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Semen is a mixture of a few different things

"Semen is a mixture of a number of things — one of the things in semen is sperm," says Dr. Caudle.

The sperm is contained in a white fluid called seminal fluid that's released by the prostate glands and seminal vesicles. Semen is a combination of both this fluid and sperm.
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People aren’t born with semen.

While people can be born with male genitalia, the accompanying semen doesn't come in until puberty.

"That’s when hormones are released and the testicles produce testosterone," Dr. Caudle explains. "And when the boy starts developing testosterone, that’s when we get all these, what we call secondary sex characteristics, voices get lower, they get hair, they get tall, they get masculine, all that kind of stuff. But in addition to that, he starts producing sperm."
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An ejaculation can contain up to 500 million sperm.

But Dr. Caudle reminds us that it only takes one for pregnancy to occur.

How does this happen? After ejaculation, the semen is deposited in the vagina. The sperm swim up the cervix and into the uterus, where they "hang out" until ovulation. If they match with an egg, then pregnancy has occurred.

And if pregnancy isn't your desired result, make sure you pick the best contraception for you and your partner.
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Pre-ejaculate contains sperm.

Not only does pre-ejaculate, or pre-cum, contain sperm, but a person isn't able to tell when they're producing it, unlike ejaculation.

"That’s why we always, as physicians, say not to rely on the pull-out method to not get pregnant," Dr. Caudle warns. "Because you actually have pre-cum, which is a little bit of sperm leaking out, that can get a woman pregnant."
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Semen is digested the same way as food.

People can choose to swallow semen, either during oral sex or otherwise. When that happens, it passes through our bodies in the same way as food.

"In terms of digestion, it makes me think of how we digest other things that go into our body," says Dr. Caudle. "I think a lot of how safe sperm digestion is probably depends on the people and what conditions they may or may not have."

Meaning: If you have a sensitive stomach, treat semen as you would any other food and proceed with caution.
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STIs can be transmitted through semen.

"Yes, you can get STDs through semen," says Dr. Caudle. More specifically, the CDC reports that HIV, chlamydia, and gonorrhea bacterias are carried in bodily fluids like semen.
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But semen is not the only way STIs are transmitted.

While semen can contain bacteria that transmits STIs, semen isn't required to facilitate the spread.

"You can also get [STIs] from blood, or vaginal fluids or other fluids," says Dr. Caudle. "But you don’t actually have to ejaculate to give or get [STIs]... Skin-to-skin contact can sometimes do it for things like herpes and genital warts."

STIs can also be contracted from oral or anal sex.
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There is (sort of) such a thing as unhealthy semen.

While there aren't too many issues with semen that manifest physically, there are certain cases in which you can tell something is wrong just by looking at it.

"It is possible for a male to have blood in his sperm," says Dr. Caudle. "It’s called hematospermia, where they have a little bit of blood in the ejaculate, and that’s something that needs to be looked into."

There could be a number of causes for blood in semen. Usually, it's due to an infection or inflammation of the prostate, urethra, epididymis, vas deferens, or the seminal vesicles. Blood in semen can also be due to vigorous sexual activity, some kind of blockage, or, less commonly, a tumor. As always, it's best to ask your doctor if you notice anything.
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A semen analysis involves more than just sperm count.

When it comes to analyzing an individual person's semen, there's a lot to consider. According to Resolve: The National Infertility Association, in addition to sperm count, doctors also study the sperm's mobility, forward progression or velocity, its size and shape, the total volume produced, and its ability to go from a gel consistency at the time of ejaculation to a more liquid state.
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There’s no single “healthy” sperm count.

A person's sperm count is simply the number of sperm present per ejaculate.

"It’s a moving target," Dr. Werthman said after I asked for a specific number. "Because every time the World Health Organization redoes its criteria, it keeps lowering and lowering and lowering it."

Resolve listed a normal sperm count as being anything from 40 million to 300 million per milliliter of ejaculate. Dr. Werthman puts the average for a healthy 20- or 30-year-old at 60 million.
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In fact, a person's sperm count changes every time it’s analyzed.

"The semen analysis is inconsistent," Dr. Werthman says. "They go up and down over the course of the year. So you can have one day where you have a count of a million, and then four months later you can have a count of 70 million."

A lot of this has to do with what's going on inside the body and the overall health of the patient. Something like having the flu can reduce sperm count drastically. There are also some environments and substances to avoid if someone is looking to raise or maintain their count.

"We know that sitting in hot tubs, heat, is bad for sperm," says Dr. Werthman. "We know that smoking’s terrible for sperm, we know that excessive drinking is terrible for sperm, marijuana is bad for sperm. So if anyone is doing those things. it may reduce their fertility potential."
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Male fertility is analyzed through a number of things, and sperm count is only one factor.

"Semen analysis is a reasonable screening test, but in and of itself, it’s not that meaningful," says Dr. Werthman.

A more important indicator of fertility is a person's history of trying to conceive.

"Have they been trying to conceive, or have they not been trying to conceive? How long have they been trying to conceive? Those kinds of things," says Dr. Werthman. "The other thing semen analysis doesn’t tell us is whether the sperm will work or not. You can have a perfectly normal semen analysis, all the parameters are fine, and not be able to get somebody pregnant. And you can have an abnormal semen analysis and be able to get someone pregnant."
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Sometimes, people can have trouble ejaculating.

Inability to ejaculate is uncommon, and is usually indicative of a health issue, like a blockage or something neurological. It's important to call your doctor if you're having an issue that concerns you.
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