In theory, anyone who is sexually active has some risk of being exposed to STIs. Practically speaking, your risk depends upon your sexual activities. People at increased risk of an STI include:
People who have unprotected sex: Having unprotected vaginal, anal or oral sex (i.e. without a condom) increases your risk of contracting an STI.
People who have multiple sexual partners: People who have multiple sexual partners have a higher prevalence of STIs.
People who have an STI: People who have one STI often have a higher chance of becoming infected with another STI.
People who inject recreational drugs: Sharing needles can spread many infections, including HIV and hepatitis (B and C).
Men who have sex with men (MSM): Gay, bisexual and other men who have sex with men (MSM) appear to have a higher prevalence of STIs.
People who engage in transactional sex: Commercial sex workers have a higher risk of contracting or having an STI.
People from countries with higher rates of STIs: Countries such as Sub-Saharan Africa, South-East Asia and Latin America/Caribbean appear to have higher rates of STIs overall.
People who use drugs during sex ("chemsex"): Using substances such as mephedrone, GHB/GBL or methamphetamine during sex can lower inhibitions and lead to more risky sex.
Young people: People aged 15 to 24 years appear to be at higher risk of STIs.