How does an STD test work? What you should know

    Updated 28 February 2024 |
    Published 17 April 2019
    Fact Checked
    Medically reviewed by Dr. Ruth Arumala, Obstetrician and gynecologist, gynecologic and cosmetic surgeon, Texas, US
    Written by Kate Hollowood
    Flo Fact-Checking Standards

    Every piece of content at Flo Health adheres to the highest editorial standards for language, style, and medical accuracy. To learn what we do to deliver the best health and lifestyle insights to you, check out our content review principles.

    Almost everyone will need to take an STI or STD test at some point, but doing one can be daunting if it’s your first time. Find out what to expect below, with advice from a Flo expert.

    Feeling nervous before a sexually transmitted infection (STI) test (sometimes known as a sexually transmitted disease or STD test) is totally understandable, especially if you’ve never had one before. 

    Whether you’re scared about what the results will say or whether the test itself will be painful or intrusive, know that all of these fears are common and very normal. 

    Finding out as much as you can before the test can help you feel more prepared. Knowledge is power, after all. So let’s get clued up on what happens at an STI test with a little help from a Flo expert.

    Talk to others who've had an STI

    In Flo's friendly and anonymous closed community, Secret Chats

    Key takeaways

    What is an STI or STD test? 

    We’ll start with the basics. The purpose of an STI test is to figure out what’s going on if you’re experiencing any STI symptoms or check whether you have an asymptomatic (symptom-free) sexually transmitted infection. 

    If you think you might have an STI, it’s natural to feel very worried and alone. But STIs are extremely common, with 1 in 5 people in the United States having a STI on any given day. 

    It may also be reassuring to know that most STIs can be completely cured — and all are treatable. It’s when STIs are left untreated that more serious health problems can develop, which is why it’s so important to get tested and follow your doctor’s treatment advice. 

    Depending on which STI you need to check for, you may have options on where you can take the test. It could be through your regular health care provider, at a public health clinic, or by simply taking an at-home test.

    Half of Americans will catch an STI*

    You're not alone. Learn more about symptoms and treatment in the Flo app. *Source: KFF

    At-home STI testing

    Taking an STI test at home can be more convenient and less nerve wracking than doing it at your doctor’s office. So it’s no surprise that at-home tests for certain types of STIs like human immunodeficiency virus (HIV), chlamydia, and gonorrhea have become more popular

    These tests usually involve taking a urine sample or a swab from either your mouth or genitals. After collecting the sample, you’ll need to mail it to a lab to be tested. 

    The downside is that at-home tests aren’t always accurate. If you get a positive result, your health care provider will need to test you again to confirm the diagnosis. Similarly, if you get a negative result but you have STI symptoms, you should speak to your doctor.

    What does an STI test involve? 

    Doing an STI test in person can be daunting if you’ve never had one before, so let’s break down exactly what to expect. An appointment will usually start with your health care provider asking some questions about your medical and sexual history. For example, they may ask

    • How many people you’ve had sex with
    • What kind of protection you’ve used 
    • If you have any symptoms

    These topics can feel super personal and awkward to talk about, but being open and honest will help your doctor give you the best possible care. Know that it’s normal for them. In fact, they probably have many of these conversations every day. They’re also bound by law to keep your medical information private, which includes your sexual history. Remember, you’re doing the responsible thing by getting tested, so the conversation is nothing to be embarrassed about. 

    Swab tests

    A swab test involves using a cotton swab to collect a sample from the vagina, anus, or urethra (the tube your urine comes out of). These types of STI tests are commonly used to look for: 

    Swab tests can also test for syphilis and herpes, but only if you have any ulcers or sores. If this is the case, your doctor may swab the ulcer or sore directly. This can be uncomfortable, but it’ll be over quickly.

    Urine samples

    Doing a urine sample involves peeing into a container. Your health care provider will give you the cup, which you can take to the bathroom. They may give you specific cleaning and collecting instructions, too. Make sure you wash your hands before and after collecting your urine, and when you’re done, take the sample back to your doctor’s office. 

    Urine tests are often used to check for: 

    Blood tests

    For some types of STIs, doctors need to check for the infection in your blood. These types of STI tests involve your health care provider taking a blood sample from a vein in your arm with a small needle. They’ll only take a small amount of blood, which will be collected in a test tube or vial. It shouldn’t hurt too much, just a sharp scratch when the needle goes into the skin. Your doctor may do a blood test to check for the following STIs:

    How long do STI tests take?

    Your sexual health appointment may take a while, as your doctor will want to chat through your medical history before they carry out the actual test. The type of test you have and whether your doctor also wants to perform a physical exam will have an impact on the time it takes too. But to give you a rough idea, at some clinics, sexual health appointments last between 30 and 40 minutes

    How long it takes to get your test results can vary. Sometimes, you can get results on the same day, but in other cases, it can take days or weeks. The wait can be really tough, so make sure you’re getting the emotional support you need from a friend or family member you can trust.

    Take a quiz

    Find out what you can do with our Health Assistant

    How do I know if I need an STI test? 

    You should get tested as soon as possible if you think there’s a chance you have an STI. “People should be screened after a new exposure (such as unprotected sex with a new partner),” says Flo expert Dr. Sara Twogood, obstetrician and gynecologist, Cedars-Sinai Medical Group, California, US. “They should also get tested if there are any concerning symptoms,” she says. Signs of an STI can include: 

    • Unusual vaginal discharge
    • Unusual vaginal bleeding
    • Pain when you pee 
    • A skin rash over your body, hands, or feet
    • Blisters, sores, genital warts, lumps, or skin growths around your genitals or anus

    But it’s important to know that STIs often have no symptoms. That’s why it’s good to get tested regularly. And if you have a new partner, it’s a good idea for both of you to get tested before having sex. It may also be good for you to discuss using barrier methods like condoms for added protection. The Centers for Disease Control and Prevention (CDC) have a handy quiz to help you figure out if you may be at risk for an STI.

    STI risk factors 

    Some people are at higher risk of catching STIs than others, such as teenagers, young adults, and men who have sex with men. 

    Dr. Twogood adds, “People with multiple sexual partners and those who do not use condoms or other barrier methods are also at higher risk. And some STIs are recommended to be screened for regardless of exposures or symptoms.” For example, the CDC recommends the following:

    • All women under age 25 should get tested for gonorrhea and chlamydia every year.
    • Women older than 25 who have new or multiple partners should be tested for gonorrhea and chlamydia every year. 
    • For men who have sex with men, HIV testing should happen once a year, along with screenings for syphilis, chlamydia, and gonorrhea. These tests should happen more frequently (every three to six months) if they have multiple or anonymous partners.

    How do I prepare for an STI test?

    Ask your health care provider if there is anything you need to do to prepare. If you’re going to have a urine or swab test, you may need to avoid using vaginal creams or douches for a while before the appointment. 

    Take a note of all your symptoms to help you make sure you get all the important information across. 

    Write down any questions you have for your doctor so that you don’t forget them when you’re there. You might want to ask them about how to talk about STIs with your partner, whether condoms provide enough protection, or if it’s worth getting retested in a few months’ time. 

    Try to mentally prepare yourself for the test by reflecting on how you’re feeling. Anxious thoughts, stress, and nerves can be very normal before taking an STI test. Speaking to someone you trust about how you’re feeling can make the experience less lonely or scary. You could even ask them to go along with you and wait outside while you see the doctor, if that would be helpful.

    What happens after you test positive for an STI?

    If you do test positive for an STI, your health care provider will tell you the next steps and recommend the best treatment. They may want to do further tests to check for complications and/or to confirm the diagnosis. 

    You should also speak to your partner or recent partners as soon as you can so they can get tested too. These conversations can be really tough, but a little preparation can go a long way. Our guide on how to tell someone they might have an STI can help you approach the conversation with more confidence

    It can be incredibly distressing to get a positive STI result, but try to remember that it’s not the end of the world. Many can be easily cured with antibiotics. And as we’ve seen, your chances of getting an STI are reasonably high as they’re incredibly common. So a positive result is definitely not a reason to beat yourself up. 

    Dealing with STIs is really just a normal part of being sexually active. By getting tested, finding treatment, and talking to your partner, you’re doing all the right things.

    More FAQs

    Should I get tested after every partner?

    It can be a good idea to get tested every time you switch sexual partners, ideally before you have sex. And if you or your partner are having sex with multiple people, it’s good practice for both of you to get tested regularly, ideally at least every six months.

    Are STI tests painful?

    STI tests are not generally painful. Some swab tests can be uncomfortable if the doctor needs to swab a sensitive part of the body, like a sore. During a blood test, you may feel a little pain when the needle first goes in, while urine tests are pain-free.

    Do all STIs show up in urine tests?

    No, some STIs need to be diagnosed via a blood test, including HIV, syphilis, and hepatitis. Meanwhile, others like genital herpes require a swab test. The STIs that can be checked for with a urine test are chlamydia, gonorrhea, and trichomoniasis.


    “Appointments.” Guy’s and St Thomas’ NHS Foundation Trust, Dec. 2023, 

    “Prepare Before You’re There.” Centers for Disease Control and Prevention, Accessed 27 Feb. 2024.

    “Chlamydia, Gonorrhea, and Syphilis.” The American College of Obstetricians and Gynecologists, Jan. 2021, 

    “How to Tell Someone That You Have an STD or STI.” Cleveland Clinic, 20 July 2021,

    “Incidence, Prevalence, and Cost of Sexually Transmitted Infections in the United States.” Centers for Disease Control and Prevention, Accessed 28 Feb. 2024.

    Nasrallah, Gheyath K., et al. “Screening and Diagnostic Testing Protocols for HIV and Syphilis Infections in Health Care Setting in Qatar: Evaluation and Recommendations.” PLOS ONE, vol. 18, no. 2, Feb. 2023,

    “STI Testing (STD Testing).” Cleveland Clinic, Accessed 27 Feb. 2024.

    “Sexually Transmitted Diseases (STDs).” Mayo Clinic, 8 Sep. 2023,

    “Sexually Transmitted Infections.” Cleveland Clinic, Accessed 27 Feb. 2024.

    “Sexually Transmitted Infections.” Office of Disease Prevention and Health Promotion, Accessed 27 Feb. 2024.

    “STD Testing: What’s Right for You?” Mayo Clinic, 14 Apr. 2023,

    “STD Tests.” MedlinePlus, 21 Sep. 2021, 

    “Which STD Tests Should I Get?” Centers for Disease Control and Prevention, Accessed 28 Feb. 2024.

    “This Is How Often You Need to Get Tested for STDs, Based on Your Relationship Status.” National Coalition for Sexual Health, 21 Oct. 2016, 

    “Urine Culture.” Cleveland Clinic,  Accessed 27 Feb. 2024.

    History of updates

    Current version (28 February 2024)

    Medically reviewed by Dr. Ruth Arumala, Obstetrician and gynecologist, gynecologic and cosmetic surgeon, Texas, US
    Written by Kate Hollowood

    Published (17 April 2019)

    In this article

      Try Flo today

      Sign up for our newsletter

      Our latest articles and news straight to your inbox.

      Thanks for signing up

      We're testing right now so not collecting email addresses, but hoping to add this feature very soon.