Facts about semen and ejaculation: what’s normal and what’s a myth

Here’s what the evidence says:

• Semen is the fluid that comes out of the penis when you ejaculate. It carries sperm, which are made in the testicles.
• Pre-cum, the fluid released before you come, can contain sperm and can carry HIV.
• STIs such as Chlamydia, Gonorrhoea and HIV can be passed on through semen.
• Changes such as blood in your semen or pain when you ejaculate are worth getting checked.

Many other claims you may have read online, about speed, taste or health benefits, have no good evidence behind them.

Semen is made in several parts of the body:

• The testicles make and store sperm.
• Sperm mature in the epididymis, a tube next to each testicle.
• When you ejaculate, a narrow tube called the vas deferens carries sperm from the epididymis to the seminal vesicles.
• The seminal vesicles and the prostate gland make the fluid that sperm travel in.

Sperm is made all the time and stored in the testicles, so men don’t have a fertile window in the way women do. Read more in “Is swallowing semen good for you?”

Not quite. Ejaculation usually happens with an orgasm, but some men have an orgasm with little or no semen coming out.

One cause is retrograde ejaculation, where semen goes backwards into the bladder instead of out through the penis. You might notice cloudy pee the first time you go to the toilet after sex. It isn’t dangerous, and men with it still feel an orgasm. It can be caused by prostate or bladder surgery, diabetes, multiple sclerosis or some medicines for high blood pressure. Read more in “Can retrograde ejaculation cause infection?”

Some popular claims about semen don’t stand up:

• Speed and distance: claims that semen leaves the body at 28 miles per hour, or can travel several feet, have no reliable source behind them.
• More semen from drinking water or pelvic floor exercises: there’s no evidence for this. NHS advice on pelvic floor exercises is about bladder control.
• Changing the taste with food: there’s no good evidence that fruit, beer, broccoli or dairy changes how semen tastes.
• Health benefits: one small study from 2002 found that female students who didn’t use condoms reported fewer signs of depression, but it couldn’t show that semen was the cause. There’s no evidence that semen improves hair or skin.

Sex without a condom raises your risk of STIs, so it isn’t worth taking chances for benefits that haven’t been proven.

Yes. Pre-cum is the fluid released from the penis before you come. It’s made by small glands called the Cowper’s glands, and it can contain sperm from a previous ejaculation, so it can lead to pregnancy. Pulling out before you come isn’t a reliable way to avoid pregnancy.

HIV can be carried in pre-cum, and fluids are often exchanged before ejaculation. If you only put a condom on just before you come, you’re not protected from STIs or pregnancy, so put it on before the penis touches the vagina or anus. Read more in “Can you pass on or catch an STI without ejaculation?”

These STIs can be passed on through semen and vaginal fluid during vaginal, anal or oral sex without a condom:

• Chlamydia
• Gonorrhoea
• HIV
• Hepatitis B, which is spread through blood and body fluids

Syphilis is passed on during vaginal, anal or oral sex through contact with a sore, and Trichomonas through vaginal sex, genital contact and shared sex toys.

Many STIs have no symptoms, so you can have one without knowing and pass it on. People with HIV who are on effective treatment and have an undetectable viral load can’t pass HIV on.

Yes. Chlamydia, Gonorrhoea, HIV and Syphilis can all be passed on through oral sex. If semen or other genital fluids come into contact with sores, cuts or inflamed areas in your mouth, infections can get into your bloodstream.

The risk of getting HIV through oral sex is much lower, but it’s higher if someone with HIV comes in your mouth and you have ulcers or bleeding gums. Read more in “Do I have an oral STI? Symptoms and testing”

See a doctor if you notice:

• Blood in your semen. It’s not usually serious and often goes away by itself in a few days or weeks, but it should be checked. Causes include infections such as a UTI or an STI.
• Pain when you ejaculate. This can be a sign of prostatitis (an inflamed prostate) or an STI such as Trichomonas.
• Unusual discharge from your penis, such as green, yellow, white or cloudy fluid, which can be a sign of an STI such as Gonorrhoea or Chlamydia.
• Little or no semen when you come, or cloudy pee after sex, which can be a sign of retrograde ejaculation.

Read more in “I have yellowish sperm. Do I have an STI?”

A semen analysis checks how many sperm you have, how well they move and their shape. Things that can lower the quality of your sperm include:

• Smoking.
• Drinking too much alcohol.
• Being overweight.
• Heat around your testicles, for example from tight underwear.
• Anabolic steroids and recreational drugs such as cocaine.

Some STIs, including Chlamydia, can also affect fertility. Sperm can survive inside the body for up to 7 days after sex. Better2Know offers a Sperm Count test at our clinics. Read more in “Can Chlamydia make you infertile?”

If you’ve had sex without a condom, testing is the only way to know if you’ve caught an STI. Better2Know offers:

• Peace of Mind: tests for Chlamydia, Gonorrhoea and Syphilis from 14 days after sex, with results in 2 days. You can book it at one of our clinics or order a home test.
• Oral Screen: a home test for Chlamydia, Gonorrhoea, Syphilis and Herpes 1 and 2, using a throat swab, a blood sample and a urine sample, from 14 days after sex, with results in 2 days.
• Full Screen: tests for 7 infections, including HIV, Hepatitis B, Chlamydia and Gonorrhoea, from 28 days after sex, with results in 3 days (5 days for the home test).

If you test before 45 days, a negative HIV result needs a repeat test. A Syphilis test in the first 3 months after sex can miss the infection, so you may need a repeat test. Not sure which test you need? Our Patient Care Team is available 24/7 on 020 7099 0955.

Can women ejaculate?

Some can. The sexual health charity Brook says people with vulvas can ejaculate, but not everyone does, and it isn’t always linked to an orgasm.

Do you still ejaculate after a vasectomy?

Yes. Once a doctor confirms the vasectomy has worked, which usually takes around 12 weeks, you no longer release sperm when you come. Use another method of contraception until then. A vasectomy doesn’t protect you or your partners from STIs, so you may still need to use condoms.

Plenty of what you read about semen online is myth. The facts that matter most for your health are simple: pre-cum can contain sperm, STIs can be passed on through semen, and changes such as blood in your semen or pain when you come are worth getting checked.

Book a Full Screen at a clinic near you or order a home test kit. Our Patient Care Team is available 24/7 on 020 7099 0955.

Not in the UK? Choose your country from the selector at the top of the page for local tests and prices.

This article originally appeared on 27 December 2013 and was last updated on 1 October 2026.

This article is general information and not a substitute for personal medical advice.

Sources

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