context: Around 1.2 million people in the U. S. have human immunodeficiency virus ( HIV) -- and more than 150,000 of them don't know it. In fact, about 30% of new HIV infections every year are transmitted by people who haven't been diagnosed. It's a good idea to be tested so you can know for sure. Everyone ages 13 to 64 years should be tested for HIV at least once, according to the CDC. All pregnant women should be tested as early in their pregnancy as possible. You should be tested at least once a year if you have any of these risk factors: You're a man who has had sex with another man You've had more than one sex partner since your last HIV test You injected drugs and shared needles You exchanged sex for drugs or money You were diagnosed with another sexually transmitted disease You had sex with someone who has HIV or whose sexual history you don't know Other things can increase your risk of HIV, so ask your doctor how often he thinks you should be tested. This is the first test you take to see if you have HIV. If the results show you're HIV positive, you'll need a second (follow-up) test to confirm it. Two common screening tests are: Antibody test: This is the most common type of HIV screening test. It doesn't look for the virus but instead looks for disease-fighting proteins (antibodies) your body makes if you have HIV. They can be found in your blood, urine, or saliva. It can take 3 to 12 weeks to make enough antibodies to tell if you have HIV. Antigen/antibody test: This screening test is also known as a combination or fourth-generation test. It looks for part of the virus (called an antigen) in your blood as well as HIV antibodies. This test can tell if there's HIV in your blood within 2 to 6 weeks of when you were exposed. Two home HIV tests that check for antibodies have been approved by the FDA. However, more than two are available on the Internet. If you buy one online, choose one of these FDA-approved tests: Home Access HIV-1 Test System: You prick your finger to get a blood sample and send it to a lab. If the result is positive, a follow-up test is done on the sample right away. You can call in to find out your results -- including the follow-up test -- as soon as the next business day. Ora Quick In- Home HIV Test: This is a "rapid result" test. It comes with a test stick and a test tube that has fluid in it. You swab your gums with the stick, then put it in the test tube. You get results in 20 minutes. If you test positive, you'll need follow-up testing at a clinic or doctor's office. The second test must be a blood test. The ones used to confirm a positive result on a screening test are: Antibody differentiation test: This is used to find out if you have HIV-1 or HIV-2. It helps your doctor know how to treat your particular virus. HIV -1 nucleic acid amplification test ( NAAT): This can tell if you have HIV in your blood as early as 7 to 14 days after you were infected. Western blot (or indirect immunofluorescence assay): Like the screening tests, this checks to see if your body has made antibodies to fight the virus. Don't let worry over an HIV test stop you from taking one. Whatever the result, it can help you make smart decisions about your body and your health: If you test positive: You can start treatment. Talk to your doctor about antiretroviral therapy ( ART). This involves a combination of HIV medicines taken every day. It won't cure HIV, but it can help you live a longer, healthier life. If you test positive: You can protect others. ART doesn't just help the person who has HIV. If you take the medication the way you're supposed to, you lower the risk of giving someone else the virus by as much as 96%. Of course, when you have HIV, you should always wear a condom during sex, and never share needles if you inject drugs. If you test negative: You can protect yourself. A negative result can remind you how important it is for you or your partner to wear a condom -- especially when you consider that 1 in 8 people with the virus don't know they have HIV. If you're HIV-negative but are afraid you were just exposed to HIV, ask a doctor about post-exposure prophylaxis, or PEP. You can take HIV medicines that can help prevent infection if you start them within 72 hours. You can find out your HIV status for free. Under the Affordable Care Act ( ACA or Obamacare), most insurance plans cover HIV testing for people ages 15 to 65 as well as others at increased risk of HIV -- and no co-pay is needed. Many clinics also offer free HIV testing. If you're concerned that a positive result will mean you can't get health insurance, ACA also ensures that you can't be denied coverage or dropped from your coverage because of HIV.