Learn about sexually transmitted infections (STIs or STDs), how they spread, and more.

Sexually transmitted infections or STIs, also called sexually transmitted diseases or STDs, can be a real threat to your health. Maintaining a healthy, and enjoyable, sex life means being aware of the risks - and knowing what to do if you think you might have an STI.

What is an STI?

A sexually transmitted infection (STI) is caused by a bacteria, virus, or parasite. There are a number of different types of STIs. They can be passed, or transmitted, between people during sex or sexual contact. Most STIs are treatable. If left untreated, some STIs can cause very serious health issues.

View the types of STIs.

How can I get an STI?

The most common way to catch an STI is through unprotected oral, vaginal, or anal sex with someone who has an STI. Unprotected sex means sex without a condom (male or female) or another barrier, such as a dental dam for oral sex. You can also catch some STIs by skin-to-skin contact, i.e. not full sexual intercourse.

Learn about safer sex.

Many STIs don’t have any symptoms. It’s important to know how to protect yourself and others.

Common STI symptoms

Many STIs share some common symptoms. These include:

  • Penis discharge
  • Changes to vaginal discharge
  • Bumps, sores, or a rash around the penis, vagina, or anus
  • Blood in your urine
  • A burning or unusual feeling when urinating
  • Pain in the pelvis or testicles
  • Pain during sexual activity and intercourse

How to know if I have an STI?

Many STIs don’t have any symptoms, or symptoms are mild or take a while to appear. That means that people can continue to have sex and pass an STI to someone else without knowing it.

The best way to find out if you have an STI is to get tested by a health care provider. That way you can receive the right treatment. Testing can be done through your doctor or at a sexual health clinic.

Learn more about testing and treatment.

How can I protect myself?

If you are having sex, the best protection against catching an STI is to use a condom and practice safe sex, e.g., through different sex activities.

Learn more about types of condoms.