Sexual health and STIs explained: testing and prevention

What STIs are and why they matter

Sexually transmitted infections are passed from one person to another mainly through unprotected vaginal, anal or oral sex, and some through close skin contact. Common ones include chlamydia, gonorrhoea, genital herpes, genital warts, syphilis, trichomoniasis and HIV. They matter because, left untreated, some can cause lasting harm — for example, chlamydia and gonorrhoea can affect fertility, and syphilis can damage many organs over time. Many STIs are becoming easier to catch as some bacteria develop resistance to antibiotics, which is another reason to test and treat early. The reassuring news is that most STIs are straightforward to diagnose and either cured or well controlled with treatment.

Symptoms — and why many cause none

One of the most important facts about STIs is that they often cause no symptoms at all, so you can have and pass on an infection while feeling completely well. When symptoms do appear, they can include unusual discharge from the vagina, penis or anus, pain or burning when passing urine, sores, blisters, lumps or itching around the genitals, unusual bleeding, or pain during sex. Because symptoms are unreliable and easy to miss or mistake, waiting for signs is not a safe way to protect your health. Regular testing — even without symptoms — is the only dependable way to know your status, particularly after a new partner or unprotected sex.

Getting tested: free and confidential

In the UK, STI testing is free and confidential through sexual health (GUM) clinics, many GP practices, and increasingly through home testing kits ordered online and posted discreetly. Testing may involve a urine sample, a swab you can often take yourself, or a blood test, depending on the infection. Chlamydia and gonorrhoea are commonly tested together, and blood tests can check for HIV and syphilis. Results are private and services are non-judgemental and welcoming to everyone, including young people and all sexual orientations and gender identities. If an infection is found, clinics also help with contacting recent partners confidentially so they can be tested and treated too.

Treatment and partner notification

Most STIs are readily treatable. Bacterial infections such as chlamydia, gonorrhoea and syphilis are cured with antibiotics, while viral infections such as herpes and HIV are managed effectively with medicines that control symptoms or, for HIV, keep the virus suppressed. It is important to complete any treatment fully and to avoid sex until you and your partner have finished treatment and been given the all-clear, to prevent passing the infection back and forth. Telling recent sexual partners so they can be tested — known as partner notification — is a key step; clinics can do this anonymously on your behalf if you prefer, helping to break the chain of infection.

Preventing STIs

Prevention is straightforward and effective. Condoms, used correctly and consistently, greatly reduce the risk of most STIs and are available free from sexual health services. Regular testing, especially with new or multiple partners, catches infections early. Open, honest conversations with partners about testing and history help everyone stay safe. Vaccination protects against some infections — the HPV vaccine, offered to young people in the UK, reduces genital warts and cancers linked to the virus, and hepatitis B vaccination is available for those at higher risk. For HIV specifically, PrEP is highly effective preventive medicine for people at higher risk. Combining these measures offers strong protection.