Do not take pre-exposure prophylaxis (PrEP) if you have HIV.
You may not need PrEP if you:
- always use condoms for sex
- only have sex with HIV-positive partners who are on treatment and have an undetectable viral load for at least 6 months
An undetectable viral load means there is only a very small amount of the virus in your body. It is so low that it cannot be picked up by standard blood tests.
When the virus is undetectable, it cannot be passed on through sex.
Your viral load needs to be checked regularly by a healthcare professional.
Tests you need before you start PrEP
If you decide to start taking PrEP, you will need to have some tests.
HIV test
You must have a laboratory HIV test before or as you start PrEP. Your GP or clinic will take a blood sample and send it to a laboratory. This test is sometimes called a 4th generation HIV test. It has a window period of around 6 weeks.
The window period is the time between a possible HIV exposure and when a test can detect HIV in your body.
You may need a repeat HIV test 45 days after starting PrEP. This is to make sure that an early infection is not missed.
If you have been exposed to HIV you may develop flu-like symptoms. These could be an early sign of HIV infection. Do not start PrEP until an HIV infection has been ruled out.
If you are starting PrEP after a course of post-exposure prophylaxis (PEP), start it straight after you finish the PEP. You should have a laboratory HIV blood test around the time you finish PEP. You should have another HIV blood test 4 to 6 weeks after starting PrEP.
Post-exposure prophylaxis (PEP)
Sometimes you will do a rapid HIV test as well as the laboratory HIV test. It may be possible to start PrEP on the day of your first PrEP appointment. Your healthcare professional will talk to you about this.
Hepatitis B test
You must have a test for hepatitis B. This is because PrEP medicines are active against both HIV and hepatitis B.
If you have hepatitis B, you can still take PrEP. But you need to take daily PrEP. You also need regular monitoring and medical advice. This is especially important when you want to stop PrEP.
Event-based dosing (EBD) is not suitable if you have hepatitis B or if you are not sure if you have it. EBD is when you take PrEP around the time of sex.
Hepatitis A and B vaccination is recommended for many PrEP users.
Kidney function tests
You need to have your kidney function checked before you start PrEP. PrEP medicines can affect your kidneys. You will have a blood test for creatine and sometimes a urine test for protein.
When you take PrEP you will have regular kidney checks.
Tests for sexually transmitted infections (STIs)
Get tested for STIs including:
- syphilis
- chlamydia
- gonorrhoea
- hepatitis C
Talk to your healthcare professional about vaccinations for HPV and mpox.
Pregnancy test
If you can get pregnant you should have a pregnancy test before starting PrEP. This may be reviewed during follow-up as needed.
PrEP is recommended if you are pregnant and at risk of HIV infection.
Monitoring while taking PrEP
When you are taking PrEP, your clinic will regularly monitor:
- for HIV and STIs
- your kidney function
Monitoring helps to find potential problems at an early stage.
Your first time taking PrEP
When you start taking PrEP, your doctor or nurse will arrange your next appointment with you.
At this appointment they will check:
- how you are managing the medicine
- if you need any more tests or vaccinations
If you are taking daily PrEP
For daily dosing, every 3 to 6 months you should have a:
- HIV blood test (laboratory test)
- test for other STIs
Some people will need a kidney function blood test.
If you are taking event-based PrEP
For event-based dosing, your appointments will depend on:
- how often you use PrEP
- your potential risk for exposure to HIV and STIs
Your PrEP team will talk to you about how often to have HIV and STI testing. They will help you make a follow-up plan.
Hepatitis C test
You should have a hepatitis C test every 12 months. You may need this more often depending on your circumstances.
Hepatitis C testing and diagnosis
Home STI and HIV testing
You may be able to use our free STI home-testing service for some of your testing follow-up. Talk to your PrEP service about this. They will tell you if it is suitable for you.