Patient education: Preventing HIV after unprotected sex or needle-sharing (The Basics)

How do you get HIV from someone who is infected? — The most likely way to get HIV from someone is to:

●Have unprotected anal or vaginal sex with them

●Share the same needle (for example, to inject drugs)

If you get blood or other body fluids in your vagina, anus, or inside the tip of your penis, you could get infected. It is also possible to get infected if blood or fluids with HIV get into your eyes or mouth, but this is less risky. It is very unlikely that you would get HIV just by getting blood or other body fluids on your skin.

Body fluids that are most dangerous include blood and the fluids that come from the penis, vagina, and anus during sex. Other body fluids are less dangerous, as long as they aren't mixed with blood. This includes urine, saliva, sweat, and tears.

Can I lower my chances of getting HIV even after being exposed to the virus? — In some cases, yes. There are treatments that can reduce your risk of getting HIV. Doctors call this "post-exposure prophylaxis," or "PEP." But for it to reduce your risk, you must start the treatment within 3 days of being exposed to the virus.

If you think you have been exposed to HIV, see your doctor or nurse right away. They can give you the best advice on what to do after an exposure. Although the risk of getting HIV after 1 exposure is often pretty low, it is always best to discuss your risk of HIV with your doctor or nurse. Do not try to figure out your risk on your own.

It is important to know that medicines to prevent HIV after exposure are not meant for people who risk getting exposed over and over again. In other words, if you often have unprotected sex or share needles when you use drugs, these treatments are not recommended. Instead, you might be able to take HIV medicines on a regular schedule to reduce the risk of getting HIV. Doctors call this "pre-exposure prophylaxis," or "PrEP." If you do this, it is very important to always remember to take the medicines and visit your doctor regularly. Ask your doctor if this type of treatment is right for you.

How likely is it that I will get HIV? — That depends on a lot of things, such as:

●How you were exposed – Some ways of getting exposed are riskier than others. For example, although it is possible to get HIV through oral sex, it is unusual. On the other hand, unprotected anal sex is very risky, and riskier than vaginal sex. Sharing needles if you use drugs is also extremely risky.

●Whether you have any sores or cuts on the part of your body that was exposed – People who have open wounds or sores are more likely to get infected. For example, if you have herpes sores on your genitals, your risk of getting HIV goes up.

●Whether the body fluids you were exposed to came from a person who is taking HIV medicines – If the person has HIV but is being treated, and their medicines are working, your risk will be extremely low. If the person has HIV and has a lot of virus in their blood, your risk of getting HIV goes up.

What will the doctor or nurse do? — First, your doctor or nurse will probably test you for HIV. This will tell them whether you were already infected with the virus in the past. (It takes a couple of weeks for the virus to show up in your blood and the test to turn positive.) If you already have HIV, it is important for you to see a doctor so you can start taking the right medicines.

If the test is negative, you and your doctor or nurse will have to decide if HIV medicines are right for you based on how likely it is that you could become infected, and on how you feel about the risks and benefits of taking medicines.

If you and your doctor or nurse decide that you should take medicines to prevent HIV infection, they will usually prescribe 3 different medicines. Sometimes, medicines are combined into a single pill. You need to start these as soon as possible and take them for a month.

If the person who exposed you doesn't know if they have HIV, and is willing to be tested, your doctor or nurse might test them too. If they can test the person right away, and the test is negative, then you won't have to take HIV medicines. However, sometimes this is not possible. If you already started the medicines, you can stop them if you find out later that the person who exposed you does not have HIV.

Your doctor might also test or treat you for other types of infections you can get through sex or by sharing needles.

What are the risks or side effects of medicines to prevent HIV? — The side effects differ depending on which specific medicines you take. In general, most patients don't have problems while taking these medicines. If you do have side effects, they might include nausea or vomiting or a rash. You should call your doctor or nurse if this happens.

If you are pregnant or could be pregnant, tell your doctor or nurse. Some medicines are not safe to take while you're pregnant, so your doctor or nurse needs to know if you are or could be pregnant.

What happens after I am done taking the medicines? — Your doctor or nurse will test you again to see if you got infected with HIV. These tests will be done 2 or 3 times after your exposure, depending on which test they use.

It is very important that you take all the medicine your doctor prescribes. Still, even if you take all your medicine correctly, there is no guarantee that you will not get infected. The medicines improve your chances, but they do not always prevent HIV. That is why it is best to not share needles or have unprotected sex in the first place.

In the weeks after your exposure, look for symptoms of HIV infection, such as:

●Fever

●Swollen glands

●Sore throat

●Sores in your mouth, penis, anus, or vagina

●Muscle and joint pain

●Diarrhea

●Headache

●Nausea or vomiting

●Weight loss

These symptoms usually happen 2 to 4 weeks after you might have been exposed. If you notice any symptoms that worry you, call your doctor or nurse.

What else should I do? — Until you know for sure whether you have HIV, make sure to use condoms during sex. Or avoid sex. Do not donate blood, sperm, or any tissues. Otherwise, if you did get HIV, you could infect someone else.

More on this topic

Patient education: HIV/AIDS (The Basics)
Patient education: Starting treatment for HIV (The Basics)
Patient education: Tests to monitor HIV (The Basics)
Patient education: Blood or body fluid exposure (The Basics)
Patient education: Sexually transmitted infections (The Basics)
Patient education: Care after sexual assault (The Basics)
Patient education: Taking medicines to prevent HIV before exposure (The Basics)

Patient education: Testing for HIV (Beyond the Basics)
Patient education: Symptoms of HIV (Beyond the Basics)
Patient education: Initial treatment of HIV (Beyond the Basics)