No condom prevents pregnancy or sexually transmitted diseases (STDs) 100% of the time. But if you and your partner are having sex, nothing protects against STDs better than a properly used condom.
For those having sex, condoms must always be used to protect against STDs even when using another method of birth control. They must be used correctly and must be used every time you have sex. Even when used correctly, condoms do not protect against infections spread from sores on the skin not covered by a condom (such as the base of the penis or scrotum).
Using a condom correctly doesn't only mean putting it on right side out. You should also:
Check the expiration date (condoms can dry and crack if they're old).
Choose condoms made of latex, which is thought to be most effective in preventing STDs. If one of you has an allergy to latex, use polyurethane condoms instead.
Keep condoms away from heat and light, which can make them more likely to break.
Only use water-based lubricants with condoms. Shortening, lotion, petroleum jelly, or baby oil can break down the condom.
Open the condom packet with your hands, not your teeth, and open it carefully so you don't tear the condom.
Choose a condom with a reservoir tip to catch semen after ejaculation. Lightly pinch the top of the condom and place it at the top of your (or your partner's) penis. This gets rid of trapped air, which can cause a condom to burst.
Roll the condom down until it's completely rolled out — if it's inside out, throw it away and start over.
When you're done, you (or your partner) should withdraw while holding the condom at the base of the penis to prevent the condom from slipping off.
If a condom breaks or slips off and you or your partner is concerned about pregnancy, call your health care provider or pharmacist to discuss emergency contraception. And both partners should be tested for STDs.
While condoms aren't perfect, if you're going to have sex, they are the best way to protect yourself.