Last updated:

Reviewed by:

Dr Bryony Henderson

, Lead GP at Livi

Medically reviewed

An STI (or sexually transmitted infection) is an infection that can be spread through sexual contact. While some infections can be easily treated, there are other more serious infections. Discover the different types of STIs, what symptoms they commonly cause and how to protect yourself against them.

What is an STI?

When someone has an STI it means they’re a carrying a microbe – a virus, parasite or bacteria – that's usually spread through sexual contact. Like with any infection, these microbes can cause symptoms in the infected area or in the wider body. Some people can be infected without showing any symptoms but can still pass the infection on. 

What’s the difference between an STI and an STD?

STI stands for sexually transmitted infection and STD stands for sexually transmitted disease. Doctors tend to use STI over STD, as STD can be misleading. 

‘Disease’ suggests a medical problem with obvious signs and symptoms, while that’s not always the case with common STIs – chlamydia and gonorrhoea can come without symptoms for example. 

So, STDs are diseases that occur as a result of having an STI. Some STIs, such as chlamydia or gonorrhoea, may not develop into an STD. 

What are the most common STIs?

There are around 30 different STIs, and 8 of these are recognised as the most common.

4 of them are bacterial or parasitic infections and can be cured easily when diagnosed early. These are:

4 of the most common viral infections are:

Viral infections are more difficult or sometimes impossible to cure. They might require lifelong treatment to reduce their impact.

What are the main causes of STIs?

1. Sexual contact

There are about 30 bacteria, viruses and parasites that can be transmitted sexually.

STIs are mainly passed on during sexual intercourse – including vaginal, anal or oral contact. This is why it’s important to use condoms during sex or for any type of penetration. 

2. Blood transmission

STIs can also spread via blood transfusions or sharing needles.

3. Transmission from mother to child

Many STIs, including chlamydia, gonorrhoea, primary hepatitis B, HIV and syphilis, can also be transmitted from mother to child during pregnancy and childbirth if the mother is infected.

What are the symptoms of STIs?

Depending on the STI, the symptoms can vary a lot. However, there are some key symptoms to look out for that can indicate an STI:

  • Fever

  • Pain in the lower tummy

  • Itching or abnormal discharge from the genitals

  • Reddening of the genitals

  • Unexpected vaginal bleeding

  • Skin rash, warts or lumps around the genitals

  • A burning sensation when peeing

Some infections are asymptomatic, so you can be infected without showing any visible signs of infection. It’s important to get tested to find out if you have been infected and, if necessary, to follow an appropriate treatment plan.

How do I know if I have an STI?

You can have an STI without realising it. Symptoms are not always visible or obvious. To find out for certain that you have an STI, you can go to the doctors or sexual health clinic to be screened. Knowing your result is the best way for you to be treated quickly and efficiently, and to avoid transmitting the STI to others.

How do you screen for STIs?

A GP or sexual health clinic can carry out an STI screening test. It's often quicker to go to a sexual health clinic and you can remain entirely anonymous if you want. 

Depending on the STI, different types of investigations can be used for diagnosis. They include:

  • Urine analysis

  • Oral swab

  • Blood test

  • Vaginal, anal or urethral swabs

What treatments are there for an STI?

STIs like chlamydia, gonorrhoea or syphilis are treated with antibiotics but you will need a prescription from a doctor.

Other STIs like genital herpes or HIV are incurable and can remain in the body for life. However, there are treatments that can relieve your symptoms or get rid of them entirely.

How can I prevent an STI?

There are simple ways to prevent and stop the transmission of STIs.

  • To protect yourself and others, use a condom every time you have sex with a partner whose STI status is unknown.

  • Get tested for STIs like HIV on a regular basis if you have multiple partners or each time you want to stop using a condom with a new, regular partner.

  • When infected, complete the full course of treatment your doctor has prescribed. For some STIs like hepatitis B and HPV it’s also possible to get vaccinated.

  • Tell your partner(s) so that they can also be tested and treated if necessary. A sexual health clinic can inform past partners, anonymously, if you want. 

When should I see a doctor?

If you’re unsure if you have an STI or you’ve had unprotected sex, it’s important to see a doctor. STIs can be detected very easily and there aren’t always visible signs. 

If you have an STI, it can be helpful to talk to a specialist who you can trust. That way, they can answer any questions you might have.

How can a Livi doctor help?

A Livi doctor can assess your situation and determine whether it’s possible you have an STI. They can help direct you to the best place to get tested and for you to get treatment.

Last updated:
Reviewed by:
Dr Bryony Henderson, Lead GP at Livi