References UK clinical guidance from the NHS, the British HIV Association (BHIVA), and the British Association for Sexual Health and HIV (BASHH). Last updated: April 2026.
You’ll see both terms — STD (sexually transmitted disease) and STI (sexually transmitted infection) — used in sexual health conversations. They’re often used interchangeably, but there’s a subtle difference. Most UK sexual health services and international health bodies now prefer “STI” because it’s more accurate and less stigmatising. Here’s why.
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The Terminology
| Term | Meaning |
|---|---|
| STI (sexually transmitted infection) | An infection transmitted through sexual contact, with or without symptoms |
| STD (sexually transmitted disease) | Disease caused by a sexually transmitted infection, typically implying symptoms or complications |
Why the Shift to STI?
Many infections have no symptoms
Chlamydia, gonorrhoea, HPV and others are often silent. A person can have the infection without showing any disease. Calling it an STI reflects this reality — you can have the infection without having a disease.
Less stigma
“Disease” carries more negative weight than “infection.” Sexual health services prefer language that encourages testing and treatment without shame.
Medical accuracy
STI describes the biological situation more precisely. STD is still valid when a condition has progressed to symptoms or complications.
Examples
- A person with chlamydia who has no symptoms has an STI
- A person with pelvic inflammatory disease caused by untreated chlamydia has an STD
- Most clinicians and services use STI to cover both situations for simplicity
What Does This Mean for You?
- If you see either term, they usually mean the same thing in practice
- Modern UK services (including this site) use STI
- Don’t assume “no symptoms” means “no infection” — testing is the only way to know
- Regular STI screening is recommended for anyone who is sexually active
Common STIs in the UK
- Chlamydia (most common)
- Gonorrhoea
- Genital herpes (HSV)
- Genital warts and other HPV-related conditions
- Syphilis
- HIV
- Hepatitis B
- Trichomoniasis
- Mycoplasma genitalium
Read more: What is chlamydia? | What is HIV? | STI testing accuracy
Frequently Asked Questions
Should I say STD or STI?
Either is understood, but STI is more accurate and is preferred by most UK sexual health services.
Is HIV an STI or STD?
HIV is an STI. It can progress to an STD (specifically AIDS) if untreated, but with modern treatment this progression is rare.
Can I have an STI without symptoms?
Yes. Many STIs cause no symptoms at all, especially chlamydia, gonorrhoea (particularly in women), HPV and early HIV. Testing is the only reliable way to know.
Related reading
- A to Z of Sex: Sexual Health Terms Explained
- Alcohol and HIV: What You Need to Know
- Anxiety and HIV: Coping and Getting Support
- Are All STIs Curable?
- Blood Problems and HIV: Anaemia, Low Platelets and More
Sources
- NHS — Sexual health conditions
- BASHH — UK clinical guidelines for STI management
- British HIV Association (BHIVA) — HIV treatment guidelines
- Terrence Higgins Trust — sexual health information
- UK Health Security Agency — STI surveillance data
Steve Page is a recognised expert on Sexually Transmitted Diseases (STDs) and STD treatments, having published numerous articles in peer-reviewed journals and presented his research at conferences around the world. He has an in-depth understanding of the latest medical research on STDs, and is an advocate for the development of new treatments and protocols to improve the health of those affected. In addition to his research, he has dedicated his career to understanding the causes and symptoms of STDs, as well as how to best treat those impacted.
