If you're sexually active, especially with multiple partners, you may have questions about the risk of getting a sexually transmitted disease (STD) and when to get tested.

Getting tested is important. That's because you can have a STD without knowing it. In many cases, there aren't any symptoms. In fact, that's why many experts prefer the term sexually transmitted infections (STIs), because you can have an infection without disease symptoms.

But what types of STI testing do you need? And how often should you be screened? The answers depend on your age, your sexual behaviors and other risk factors.

Don't assume that you're receiving STI testing every time you have a pelvic exam or Pap test. If you think that you need STI testing, talk to your health care provider. Tell your provider about your concerns and what tests you would like or need.

These guidelines for specific STIs can help you decide if STI testing is right for you.

Chlamydia and gonorrhea

National guidelines recommend yearly screening for:

• Sexually active women under age 25
• Women older than 25 and at increased risk of STIs — such as having sex with a new partner or multiple partners
• Men who have sex with men
• People with HIV
• Transgender women who have sex with men
• People who have been forced to have intercourse or engage in sexual activity against their will

Health care providers screen people for chlamydia and gonorrhea using a swab test or urine test. The sample is then studied in a lab. Screening is important, because if you don't have symptoms, you may not know that you're infected.

HIV, syphilis and hepatitis

The U.S. Preventive Services Taskforce encourages HIV testing, at least once, as a routine part of health care if you're between the ages of 15 and 65. Younger teens or older adults should be tested if they have a high risk of an STI. The Centers for Disease Control and Prevention (CDC) advises at least yearly HIV testing if you're at high risk of infection.

National guidelines recommend hepatitis B screening for people age 18 and older at least once, and with a test that includes a few different markers of the virus. Guidelines also recommend hepatitis C screening for all adults. Vaccines are available for hepatitis A and B and are usually given at birth. Unvaccinated adults can be vaccinated if they are at high risk of getting hepatitis A or B.

If you have any of the following risk factors, talk to your health care provider about testing for HIV, syphilis or hepatitis:

• Symptoms of infection
• Positive test for another STI, which puts you at greater risk of other STIs
• Having more than one sexual partner, or if your partner has had multiple partners, since your last test
• Intravenous (IV) drug use
• Newly diagnosed hepatitis C infection
• Having been in jail or prison
• Men who have sex with men
• Being pregnant or planning to become pregnant
• Being forced to have intercourse or engage in sexual activity against your will

Your health care provider tests you for syphilis by taking either a blood sample or a swab from any genital sores you might have. A lab specialist studies the sample in a lab. Your provider also takes a blood sample to test for HIV and hepatitis.

Genital herpes

Providers generally only recommend testing for genital herpes for people who have symptoms or other risk factors. But most people with herpes never have any symptoms but can still spread the herpes virus to others. Your health care provider may take a tissue sample or culture of blisters or early ulcers, if you have them, and send them to a lab. But a negative test doesn't always mean you don't have herpes, especially if you have symptoms.

A blood test also may tell if you had a past herpes virus infection, but results aren't always reliable. Some blood tests can help providers see which of the two main types of the herpes virus you have. Type 1 is the virus that usually causes cold sores, although it can also cause genital sores.

Type 2 is the virus that causes genital sores more often. Still, the results may not be clear, depending on how sensitive the test is and the stage of the infection. False-positive and false-negative results are possible.

HPV

Certain types of human papillomavirus (HPV) can cause cervical cancer. Other types of HPV can cause genital warts. Many sexually active people get HPV at some point in their lives but never have symptoms. Most of the time, the virus goes away on its own within two years.

Regular HPV testing isn't recommended for men. Instead, health care providers may choose to test men who have symptoms, such as genital warts. A sample of the wart is removed and sent to a lab. In women, HPV testing involves:

• Pap test. Pap tests, which check the cervix for irregular cells, are recommended every three years for women between ages 25 and 65.
• HPV test. Women between ages 25 and 65 should have an HPV test alone or an HPV test along with a Pap test every five years if previous test results were within the standard range. Testing may take place more often for those who are at high risk of cervical cancer or those who have irregular results on their Pap or HPV tests.

HPV is also linked to cancer of the vulva, vagina, penis, anus, and mouth and throat. Vaccines can protect both men and women from some types of HPV. But they're most effective when given between ages 9 and 26.

At-home test kits for certain STIs, such as HIV, chlamydia and gonorrhea, have become more common and popular. For home STI testing, you collect a urine sample or an oral or genital swab and then send it to a lab.

Some tests need more than one sample. The benefit of home testing is that you can collect the sample in the privacy of your home without the need for a pelvic exam or office visit.

However, tests done on samples you collect yourself may not always be accurate. If you test positive for an STI on a home test, contact your health care provider or a public health clinic to confirm the test results. If your home test results are negative but you have symptoms, contact your provider or a public health clinic to confirm the results.

If you test positive for an STI, consider additional testing. Then get treatment from your health care provider if needed. In addition, inform your sex partners. Your partners need to be tested and treated, because you can pass some infections back and forth.

Expect to feel many emotions. You may feel ashamed, angry or afraid. It may help to remind yourself that you've done the right thing by getting tested so that you can inform your partners and get treated. Talk with your health care provider about your concerns.