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What Is An STI?

Man and woman hold each other in the dark

Sexually transmitted infections are passed between people through unprotected sex or genital contact. Recognising STI symptoms early is important to ensure you can get tested and treated as quickly as possible. This article examines STI symptoms, lists the common STIs, and offers detail on STI tests and treatments.

STI Symptoms

Not all STIs cause noticeable symptoms but you should certainly be aware of the common ones. Some STIs, like chlamydia, can be asymptomatic - i.e. they display no symptoms but can cause long-term complications like infertility. If you display any of the symptoms listed below, get a check-up as soon as possible. Our online Sexual Health Clinic offers reliable and discreet STI tests, treatment and more.

STI symptoms in both genders

  • pain when urinating
  • itching, burning or tingling around the genitals
  • blisters, sores, lumps or a rash around genitals or anus


STI symptoms in women

  • yellow or green vaginal discharge
  • smelly discharge (often fish-like)
  • bleeding between periods
  • bleeding after sex
  • pain during sex
  • stomach pain


STI symptoms in men

  • discharge from penis tip
  • irritation of the urethra
  • swollen testicles

If you have any of these symptoms you should get tested. If you recently put yourself at risk of catching an STI (e.g. through unprotected sex with a new partner) you should also get tested, even if you display no symptoms. If you have severe symptoms such as pain, abdominal pain or swollen testicles then you should see a doctor without delay.

Common STIs

Below are the most common STIs in the UK. This isn’t a complete list but covers the STIs you’re most likely to catch. For more information on each STI, click on their name.


STI Test

If you think you might have an STI you must get tested. (If you have severe symptoms then see a doctor without delay.) Visit your GP or local GUM clinic to pick up an STI test. Alternatively, you can order a test online from our online doctor service. The test is delivered to your home, then posted to our laboratory without the need for a face-to-face appointment. Visit our online Sexual Health Clinic for more information. 


STI Treatment

STIs such as chlamydia and gonorrhoea should clear up quickly once treated, although reinfection can occur. Each STI requires a different treatment. For more information visit our STI Treatment page.