Pre-Exposure Prophylaxis (PrEP)

Pre-Exposure Prophylaxis (PrEP) is used to reduce the risk of getting HIV (human immunodeficiency virus).

PrEP works by stopping HIV from getting into your body and making copies of itself (replicating). You'll only be protected from HIV infection if there are high enough levels of PrEP in your body, so it's important to take it correctly.

PrEP can be used by anyone from a community or group that is most at risk of HIV, or people who have sex with people from those networks.

You may benefit from taking PrEP if:

• you're an HIV-negative man having condomless sex with men, and other people who have sex within these networks
• you have a partner (or ex-partner) with HIV
• your partner (or ex-partner) comes from a country with high rates of HIV
• you have condomless sex with a partner(s) and do not know their HIV status
• you're a trans or non-binary person and are regularly having condomless sex
• you exchange sex for money, drugs, shelter or another reason
• you are injecting drugs

Find out more about who is at risk of getting HIV.

Find out more about other at-risk activities.

PrEP comes as tablets that contain 2 medicines called tenofovir disoproxil and emtricitabine. Both medicines are often also used to treat HIV.

You can get PrEP from a health professional at an NHS sexual health clinic.

Most adults and young people aged 16 years old and over who are HIV-negative can take PrEP. It may sometimes be prescribed for people below 16 who are at risk of HIV. PrEP should not be prescribed to anyone below the age of 12 years.

PrEP is not suitable for some people.

To make sure it's safe for you, tell the clinic doctor if you:

• have ever had an allergic reaction to tenofovir disoproxil, emtricitabine or any other medicine
• have severe liver or kidney problems
• are pregnant or breastfeeding
• have a weakened immune system (immunocompromised)
• are HIV positive
• have hepatitis

You may not need to take PrEP if:

• your partner is HIV-positive, takes HIV medicine and has an undetectable viral load – this is when the level of HIV in your body is low enough not to be detected by a HIV test
• you always wear condoms when you're having sex.

Condoms can sometimes split. Find out more about what to do if your condom splits.

Taking PrEP daily provides protection for vaginal/frontal and anal sex.

How to take it

Take 1 tablet every day, around the same time each day. Wait 7 days after you start taking it before you have sex.

If you want to start taking daily PrEP but think you may have sex within the first 7 days, take 2 tablets at least 2 hours before you have sex. Then continue to take 1 tablet each day.

It's better to take PrEP with or after food.

If you're sick (vomit) within 1 hour of taking PrEP, take another tablet. If you're sick more than 1 hour after taking PrEP, do not take another tablet.

If you have difficulty swallowing tablets, you can crush PrEP and mix it with a drink of water, orange juice or grape juice.

If you forget to take it

If you take PrEP every day and miss your dose, you can still take it as long as it's within 12 hours of when you were supposed to take it. If it's longer than 12 hours, you'll have to miss that dose and take the next one at the usual time.

It's important not to miss your dose but if that does happen, it's OK. However, for full protection, you must have taken at least 6 daily doses in the past week.

If you miss more than 2 of your doses in a week, ask the doctor at your clinic for advice.

If you do not take your PrEP tablets for a week or more, you'll have to start again. Do not take more than 2 tablets when you start PrEP.

Do not take more than a total of 7 pills in 1 week, unless you started with 2 doses.

If you forget doses often it may help to set an alarm to remind you. You could also ask your pharmacist for advice on other ways to help you remember to take your medicine.

If you forget to take your PrEP doses often, you can use the PrEP time tracking app to set tablet reminders and track your daily or on-demand doses.

If you have had vaginal/frontal sex, take your daily dose (1 tablet) for 7 more days after the last time you had sex. It is then OK to stop.

If you have had anal sex, take your daily dose (1 tablet) for 2 more days after the last time you had sex. It is then OK to stop.

Taking PrEP on demand will give you protection against HIV during anal sex.

PrEP on demand is not recommended for vaginal/frontal sex.

Do not use on-demand dosing if you have hepatitis B because PrEP can affect the hepatitis B virus. Starting and stopping PrEP can make the virus more active and this can lead to liver inflammation.

How to take PrEP on demand

If you want to take PrEP on demand, follow these steps:

• take 2 tablets between 2 and 24 hours before having anal sex
• take 1 tablet 24 hours later
• take 1 tablet 24 hours after that

If you're continuing to have sex over a period of time, carry on taking 1 pill every 24 hours until you have not had sex for 2 days.

If you have difficulty swallowing tablets, you can crush PrEP and mix it with a drink of water, orange juice or grape juice.

Stopping PrEP on demand

If you have had anal sex, take your daily dose for 2 more days after the last time you had sex. It's then OK to stop.

Check with your clinic before stopping. Stopping taking this medicine or missing doses may increase your risk of getting HIV infection.

As long as you have regular tests, you can take PrEP for a long time.

Before you start taking PrEP, you'll be recommended to have:

• a test for HIV and other STIs – you'll need to continue to have these regularly, for example, every 3 months
• a hepatitis B test – to confirm you do not have a hepatitis B infection
• a blood test to check your kidney function – using PrEP can reduce kidney function, so it's important to know if you have pre-existing kidney issues or are taking medicine that may affect your kidneys

If you are over 40 or already have issues with your kidney function, you may need more regular kidney function tests. Check how often you need to do this with your clinic doctor.

If your doctor has any concerns about your blood test results, they may talk to you about stopping PrEP treatment.

If you have been taking PrEP for 7 days, you are still protected, even if you miss the occasional dose.

If you have been taking PrEP daily, you must have taken at least 6 doses in the past week to still be protected.

• you take 3 PrEP tablets or more at the same time

Go to 111.nhs.uk or call 111

If you need to go to A&E, do not drive. Ask someone to drive you or call 999 and ask for an ambulance.

Bring the PrEP packet or leaflet inside it, any remaining medicine, and any other medicines you take.

These common side effects of PrEP may happen in more than 1 in 100 people. There are things you can do to help cope with them:

Stick to simple meals and do not eat rich or spicy food. It might help to take your PrEP after you've eaten. Taking it just before bed can also help to avoid feeling sick.

If you really need to, you can take anti-sickness tablets. Ask a pharmacist which type is suitable for you.

If you're sick within 1 hour after taking PrEP, take another tablet. If you're sick more than 1 hour after taking PrEP, do not take another tablet.

If you're being sick, try small frequent sips of water to avoid dehydration. Signs of dehydration include peeing less than usual or having dark, strong-smelling pee.

If you take the combined contraceptive pill or progestogen-only pill and you're being sick, your contraception may not protect you from pregnancy. Check the pill packet for advice.

Try not to eat too much of foods like lentils, peas, beans and onions as they can cause wind. Eat smaller meals, eat and drink slowly, and exercise regularly.

There are pharmacy medicines that can also help, such as charcoal tablets or simeticone. You can also try peppermint oil capsules or drinking peppermint tea. You could also try taking an antacid for indigestion. Speak to a pharmacist for advice.

Drink plenty of water by having small frequent sips to avoid dehydration. Signs of dehydration include peeing less than usual or having dark, strong-smelling pee. Do not take any other medicines to treat diarrhoea without speaking to a pharmacist or doctor.

If you get severe diarrhoea and it lasts more than a few days, contact your clinic for advice.

If you take contraceptive pills and you have severe diarrhoea for more than 24 hours, your contraception may not protect you from pregnancy. Check the pill packet for advice.

Make sure you rest and drink plenty of fluids. Do not drink too much alcohol.

You can take paracetamol or ibuprofen as long as you have not been told to avoid these. Tell your clinic if you are regularly taking ibuprofen or diclofenac for pain or headaches as these can affect your kidneys.

Stop what you're doing and sit or lie down until you feel better. Do not drive, cycle or use tools or machinery if you're feeling dizzy or weak. Do not drink alcohol as it may make you feel worse.

If you're taking daily PrEP, take your tablet in the morning to avoid sleep problems at night.

If this advice does not help and the side effects bother you or do not go away, visit your clinic for advice.

Very few people taking PrEP have serious problems.

PrEP can sometimes affect your kidneys. This is why kidney tests are done before and during treatment.

PrEP is more likely to affect your kidneys if you're 50 or above and already have kidney problems.

It can also affect your bone health, particularly if you have bone mass density loss (BMD), but this is rare. The risk also stops once you stop taking PrEP.

Serious allergic reaction

In rare cases, it's possible to have a serious allergic reaction (anaphylaxis) to PrEP.

Call 999 now if:

• your lips, mouth, throat or tongue suddenly become swollen
• you're breathing very fast or struggling to breathe (you may become very wheezy or feel like you're choking or gasping for air)
• your throat feels tight or you're struggling to swallow
• your skin, tongue or lips turn blue, grey or pale (if you have black or brown skin, this may be easier to see on the palms of your hands or soles of your feet)
• you suddenly become very confused, drowsy or dizzy
• someone faints and cannot be woken up
• a child is limp, floppy or not responding like they normally do (their head may fall to the side, backwards or forwards, or they may find it difficult to lift their head or focus on your face)

You or the person who's unwell may also have a rash that's swollen, raised, itchy, blistered or peeling.

These can be signs of a serious allergic reaction and may need immediate treatment in hospital.

These are not all the side effects of PrEP. For a full list, see the leaflet inside your medicine packet.

PrEP can be taken during pregnancy, as it is not thought to be harmful to the baby.

If you are trying to get pregnant or are already pregnant, talk to your doctor about the risks and benefits of continuing PrEP. Do not stop taking it without speaking to your doctor.

If your doctor or health visitor says your baby is healthy, you can take PrEP daily if you are breastfeeding.

PrEP passes into breast milk in very small amounts and it is unlikely to cause any side effects in your baby. However, some babies have had mild diarrhoea.

If you become HIV positive, your clinic will discuss the options with you.

Talk to your health visitor, midwife, doctor or pharmacist as soon as possible if you have any concerns, including if your baby:

• is not feeding as well as usual or is not putting on weight
• has a tummy upset, for example diarrhoea or being sick
• has difficulty sleeping

There is no evidence to suggest that taking PrEP reduces fertility in either men or women. However, speak to your clinic doctor if you are trying to get pregnant.

Tell your doctor if you're:

• trying to get pregnant
• pregnant
• breastfeeding

Some medicines and PrEP can affect each other and increase your risk of side effects.

Tell your clinic doctor if you're taking any of these medicines before taking PrEP:

• ibuprofen or diclofenac – non-steroidal anti-inflammatory drugs (NSAIDs) that can affect the kidneys
• sofosbuvir, ledipasvir or any other medicine used to treat hepatitis C

Also tell your doctor if you're taking anabolic steroids, as these can raise your cholesterol levels.

It's OK to take PrEP if you are also taking gender-affirming hormones.

If you are a trans woman taking PrEP, hormones can lower the levels of PrEP slightly but not enough to affect your PrEP treatment.

If you take creatine as part as a fitness supplement, it can affect the results of your kidney function tests. Taking this supplement can make it look as though you have higher levels of creatine in your body and that your kidneys are not functioning normally. This may affect whether you can take PrEP or not.

If you're using creatine, let your clinic doctor know.

There's not enough information to say that herbal remedies and supplements are safe to take with PrEP. They're not tested in the same way as pharmacy and prescription medicines.

Tell your doctor or pharmacist if you're taking any other medicines, including herbal remedies, vitamins or supplements.