Doctors have their own opinions about who should be tested for which sexually transmitted disease (STD), but it's really up to you.
When official recommendations are made, they're based on research statistics about sexual activity and infection rates. But experts say the best strategy is for individuals to educate themselves and then ask for tests based on their own sexual history and level of concern.
That said, here are some basic STD testing guidelines.
If You're Sexually Active
The federal Centers for Disease Control and Prevention (CDC) recommends HIV tests for all sexually active adults and pregnant women. Urine tests are available now for chlamydia and gonorrhea, making testing easier than ever before. Some doctors recommend regular testing for both infections if you fall into one of a few high-risk groups, but anyone can request these tests.
If You're Under 24
According to a 2006 CDC surveillance report, young people ages 15 to 24 represent just 25 percent of the sexually active population but they also represented almost 50 percent of new STD cases that year.
"Young people ought to get tested once a year for HIV, syphilis, chlamydia, and gonorrhea," says H. Hunter Handsfield, M.D., a clinical professor of medicine at the University of Washington and a nationally recognized STD expert who has helped develop HIV testing guidelines for the CDC.
However, he adds that depending upon a person's sexual behavior, testing might be as frequent as once every few months, or as rare as once every two years in the case of a monogamous relationship.
Chlamydia is a crucial test for young women (though you probably have to ask for it) since it's so common and so destructive. "That's the single STD that is most likely to be present in someone who doesn't show symptoms -- and that can do a lot of damage," says Dr. Handsfield.
If You're A Man Who Has Sex Only With Women
Most doctors don't test heterosexual men for STDs other than HIV unless they have symptoms. That's partly because women get more severe health problems from HPV and chlamydia, and also because until recently STD tests have involved painful swabbing.
But chlamydia can affect male fertility, and now that there are painless urine tests for both chlamydia and gonorrhea, it may make sense to ask for these tests when you visit the doctor.
Depending on your sexual activity, the infection rates in your community, and your level of concern, you may want to be tested for syphilis as well.
If You're A Man Who Has Sex With Men
Testing for HIV and syphilis is especially important in this group because there are high rates of both infections among the men you're likely to have as partners. Depending on the number of partners you have, you may need to consider screenings more than once a year, says Dr. Handsfield.
Chlamydia and gonorrhea are also prevalent, and you can request the new urine tests instead of having to undergo an uncomfortable swabbing of your urethra.
If You're A Woman (Of Any Sexual Preference)
In addition to getting tested for HIV, all women should get annual Pap smears to make sure there are no (potentially precancerous) abnormalities in the cells of the cervix, possibly caused by HPV.
Women under 26 should also get the HPV vaccination, says Dr. Handsfield. And Jeanne Marrazzo, M.D., an STD specialist at the University of Washington medical school, advises annual chlamydia tests for younger women. "If you have multiple partners, you may want to be screened more often," she adds.
Since chlamydia can be detected with a simple urine test now, a full pelvic exam isn't necessary. You can also request a gonorrhea test at the same time, if you are concerned that you may have been exposed.