If you are old enough to have sex, you are old enough to be smart about avoiding sexually transmitted diseases (STDs). STDs affect 12 million Americans each year, and many of them are between the ages of 15 and 24.

The most common STD is chlamydia. It can be treated easily with antibiotics, but first you have to know you have it. Sometimes, early in the infection, there are no symptoms, so you don’t find out about it until you are tested. If you are sexually active, speak to your physician about being tested for chlamydia and other STDs.

Left untreated, chlamydia can cause serious problems in females such as pelvic inflammatory disease (PID), infertility, ectopic (tubal) pregnancy, and chronic pelvic pain. CDPHP recommends that sexually active females be tested for chlamydia every year and upon diagnosis of pregnancy.

In a male, symptoms may be itching and/or burning during urination and a discharge from the penis. Longer term, it can lead to an infection of the testicles and infertility.

HIV is also spread through sexual contact, but you can’t tell whether a person has HIV just by looking at him or her. If you don’t know your partner’s HIV status, make sure to use a condom when having sex. If you are in a committed relationship and want to stop using condoms, both you and your partner should first be tested for HIV and other STDs.