9 minutes read9 minutes readSummary:
- Common STI symptoms include unusual discharge, pain when peeing, itching, a rash, unusual vaginal bleeding, and lumps, blisters or sores around your genitals or anus.
- Many STIs cause no symptoms at all, and many of these symptoms can also be caused by things that aren’t STIs, such as thrush or a urinary tract infection (UTI). A test is the only way to know.
- If you have discharge, discomfort or pain when you pee, the Better2Know Comfort Screen tests a urine sample for 8 infections, including Chlamydia, Gonorrhoea and Trichomonas, from 14 days after sex, with results in 2 days.
Noticed something different down there? It’s natural to worry about what it means. Some STIs cause clear symptoms, many cause none at all, and a lot of the signs people worry about turn out to have other causes.
In this blog, we explain the STI symptoms to look out for, how they differ between infections, what else they could be and when to get tested.
What are the most common STI symptoms?
The NHS lists these as possible symptoms of an STI:
- unusual discharge from your vagina, penis or anus
- pain when peeing
- lumps or skin growths around your genitals or anus
- a rash
- unusual vaginal bleeding
- itchy genitals or anus
- blisters, sores or warts around your genitals or anus
- warts in your mouth or throat, although this is very rare
Many STIs have no symptoms, so you can have one without knowing and pass it on. If you notice any of these signs, or a partner tells you they have an STI, it’s worth getting tested.
Can you have an STI without any symptoms?
Yes, and it’s very common. How often an STI causes no symptoms depends on the infection:
- most people with Chlamydia have no symptoms
- only about 1 in 3 people with Herpes know they have it
- 10% to 50% of women and 15% to 50% of men with Trichomonas have no symptoms
- most people with Hepatitis B or Hepatitis C have no symptoms, or only mild ones
Gonorrhoea is different in men. UK guidelines say over 90% of men with an infection in the penis get symptoms, usually 2 to 5 days after sex. But infections in the throat and bottom usually cause no symptoms, in anyone.
Feeling fine doesn’t mean you’re clear. UK guidelines recommend an STI test every year if you’re sexually active, and after a new partner. Read more in “Chlamydia symptoms in men vs women: what’s the difference?”
STI symptoms in women
STI symptoms that can affect anyone with a vagina include:
- discharge that isn’t normal for you, for example yellow, green or frothy
- bleeding after sex or between periods
- pain or burning when you pee
- pain in your lower tummy, or pain deep inside during sex
- itching, soreness, swelling or redness in or around your vagina
Pain in your lower tummy can be a sign of pelvic inflammatory disease (PID), an infection of the womb, fallopian tubes and ovaries that’s usually caused by STIs such as Chlamydia and Gonorrhoea.
Changes in discharge are common, and they aren’t always caused by an STI. Read more in “Vaginal discharge: what’s normal and when to worry”
STI symptoms in men
STI symptoms that can affect anyone with a penis include:
- discharge from the tip of your penis, which may be white, cloudy or watery
- pain or burning when you pee
- pain, swelling or tenderness in your testicles
- burning or itching around your penis
- needing to pee often, or pain when you ejaculate, which can be signs of Trichomonas
Pain and swelling in the testicles can be a sign of epididymitis, an infection that’s usually caused by an STI such as Chlamydia or Gonorrhoea in men under 35.
Sudden, severe pain in a testicle is an emergency. It can mean the testicle has twisted (testicular torsion), so call 999 straight away.
Symptoms in your bottom, throat or eyes
STIs don’t only affect the genitals. Chlamydia and Gonorrhoea can infect the bottom, throat and eyes through anal or oral sex, or contact with semen or vaginal fluid. Possible signs include:
- pain, itching, bleeding or discharge from your bottom
- a sore throat, although throat infections usually cause no symptoms
- red, painful eyes with discharge
Most infections in the bottom and throat cause no symptoms, and a urine test won’t find them. If you’ve had anal or oral sex, you may need a swab from your bottom or throat. Read more in “Do I have an oral STI? Symptoms and testing” and “How do I know if I have an anal Gonorrhoea infection?”
Symptoms of each STI and when they start
Different STIs cause different symptoms, and they can take days, weeks or even years to appear:
| Infection | Possible symptoms | When symptoms can start |
| Chlamydia | Discharge, pain when peeing, bleeding after sex or between periods, pain in the testicles | 1 week to several months after infection |
| Gonorrhoea | Discharge, burning pain when peeing, pain in the lower tummy, sore testicles | Usually around 2 weeks, or 2 to 5 days for an infection in the penis, but sometimes months later |
| Trichomonas | Yellow-green discharge that may be frothy or smell fishy, soreness or itching, pain when peeing | 5 to 28 days, but sometimes much later |
| Genital Herpes | Tingling or itching, then small blisters that burst to leave sores | Usually 2 to 12 days, but sometimes months or years |
| Syphilis | A small, usually painless sore, then a rash on the palms and soles, flu-like symptoms or white patches in the mouth | 3 weeks or more, with later symptoms up to 3 months after that |
| Genital warts | Small, rough lumps that may itch or bleed but don’t usually hurt | A few weeks or months |
| HIV | A short flu-like illness with a sore throat, high temperature or rash, then often no symptoms for years | Around 2 to 6 weeks |
| Hepatitis B | Often none, but sometimes tiredness, tummy pain, dark pee or yellowing of the skin and eyes | 40 to 160 days, if at all |
| Mpox | A high temperature and aches, then a rash of spots that turn into sores or blisters, which can be on the genitals or anus | 5 to 21 days |
Mycoplasma genitalium can cause discharge and irritation in men, and bleeding after sex in women, but most people with it have no symptoms.
Symptoms alone can’t tell you which STI you have, because many of them overlap. Read more in “Genital warts: symptoms, causes and treatment”
What else could your symptoms be?
Many of these symptoms have causes that aren’t STIs:
- thrush, a yeast infection that causes itching, soreness and thick white discharge
- bacterial vaginosis (BV), which causes thin discharge with a strong fishy smell
- a UTI, which causes burning when you pee, needing to pee more often and sometimes blood in your pee
- harmless lumps, such as pearly penile papules and Fordyce spots, which are normal
- piles, threadworms and skin conditions such as eczema or psoriasis, which can cause an itchy bottom
Thrush and BV aren’t classed as STIs, although sex can trigger them. Blood in your pee isn’t a usual STI symptom, and it should always be checked by a doctor straight away.
Don’t try to diagnose yourself. The same symptom can have several causes, and an STI can look like something else. Read more in “Thrush or STI: how to know the difference” and “Are pearly penile papules (PPP) a sign of an STI?”
When should you get urgent help?
Get medical help straight away if you have symptoms of an STI and:
- severe pain low in your tummy, or tummy pain with heavy bleeding from your vagina, a high temperature, dizziness or being sick, which can be signs of PID
- sudden, severe pain in a testicle, or testicle pain with tummy pain, feeling sick or being sick
- red, painful eyes, a high temperature, painful or swollen joints or a spotty rash, which can be signs of a more serious Gonorrhoea infection
Call 999 if the pain is severe or getting worse. If you think you’ve been exposed to HIV in the last 72 hours, get urgent medical care about PEP, emergency medicine that can stop you getting infected.
Don’t wait for an STI test if you have any of these signs.
What happens if an STI isn’t treated?
Most STIs are easy to treat once they’re found, but if they aren’t treated, some can cause lasting problems:
- Chlamydia and Gonorrhoea can cause PID, which can lead to long-term pelvic pain, ectopic pregnancy and fertility problems
- Chlamydia and Gonorrhoea can also infect the testicles, and Chlamydia can cause painful joints (reactive arthritis)
- Syphilis can damage the heart, brain and nerves years later, and can pass to a baby during pregnancy
- HIV damages the immune system if it isn’t treated
Treating an STI early also stops you passing it on. Read more in “Which STIs can’t be cured? Herpes, HIV, Hepatitis B and HPV”
When should you get tested?
If you have symptoms, get tested as soon as you can, and don’t have sex without a condom until you’ve been checked. If you don’t have symptoms but have had sex without a condom with a new partner, you can test:
- for Chlamydia and Gonorrhoea from 2 weeks after sex
- for HIV with a lab test, which is reliable from 45 days after sex
- for Syphilis, with a repeat test 3 months after sex
Some tests can be taken earlier, but a negative result may need repeating.
A test is the only way to know whether your symptoms are caused by an STI. Read more in “Which STIs can be checked with a blood test?”
Which test do you need?
The right test depends on your symptoms. Better2Know offers:
- Comfort Screen: for discharge, discomfort or pain when you pee, it tests a urine sample for Chlamydia, Gonorrhoea, Trichomonas, Gardnerella, Herpes 1, Herpes 2, Mycoplasma and Ureaplasma, from 14 days after sex, with results in 2 days (3 days for the home test).
- Blemish Screen: for a sore, blister, lump or wart, it tests swabs from the affected area for Herpes 1, Herpes 2, HPV and Syphilis, with results in 5 days. You can also order a home test kit.
- Chlamydia and Gonorrhoea (Rectal Swab): for symptoms in your bottom, or from 14 days after receptive anal sex, it tests a swab from your bottom, with results in 2 days.
- Platinum Screen: tests for 12 infections, including HIV, Syphilis, Hepatitis B and Hepatitis C, from 28 days after sex, with results in 3 days.
You can book any of these at one of our clinics. 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.
FAQs
Can STI symptoms come and go?
Yes. Herpes outbreaks come and go, and Syphilis symptoms can disappear on their own while the infection stays in your body. Symptoms going away doesn’t mean an infection has cleared, so it’s still worth getting tested.
How soon after sex do STI symptoms appear?
It depends on the infection. Gonorrhoea can cause symptoms within days in men, Syphilis can take 3 weeks or more, and genital warts can take months. Some people never get symptoms at all.
Can I tell which STI I have from my symptoms?
Not reliably. Many STIs cause similar symptoms, such as discharge or pain when you pee, and some symptoms are caused by infections that aren’t STIs. A test is the only way to find out.
Final thoughts
STIs can cause discharge, pain when you pee, sores and other symptoms, but many cause none at all, and some symptoms turn out to have other causes. If you’ve noticed something new, or you’ve had sex with a new partner, a test is the only way to know.
Book a Comfort Screen at a clinic near you or order a home test kit. Our Patient Care Team is available 24/7 on 020 7099 0955.
About this article
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This article originally appeared on 11 May 2018 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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