Do not take 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 load for at least 6 months
An undetectable viral load is when the virus exists in such small amounts that it cannot be detected by standard blood tests. It means the level of HIV in your body is so low, it cannot be passed on. You need to have your viral load monitored regularly by a healthcare professional.
Tests you need before you start PrEP
If you decide to start taking PrEP, there are tests that you will need first.
HIV test
You must have a 4th generation (laboratory) HIV test before or as you start PrEP. A blood sample is usually taken from your arm, and sent to a laboratory. This test has a window period of around 45 days (around 6 weeks).
The window period is the time between a possible HIV exposure and when a test can detect HIV in your body. During the window period, you could have HIV but still have a negative HIV test.
You may need a repeat HIV test 45 days after starting PrEP. This is to make sure that an early infection is not missed.
Testing and the window period
If you may have been exposed to HIV you may develop flu-like symptoms. These could be an early sign of HIV infection. This is sometimes called seroconversion. It is when the immune system produces antibodies in response to a recent HIV infection. In this situation, you should not start PrEP until HIV infection has been ruled out. Your healthcare professional will explain this to you.
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 4th generation HIV blood test around the time you finish PEP. You should have another HIV blood test 4 to 6 weeks after starting PrEP.
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.
HIV testing and diagnosis
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 take PrEP and you have undiagnosed hepatitis B, it can be harmful to you.
You can still use PrEP if you have hepatitis B, but it needs to be used more carefully.
If you have hepatitis B, you need to take daily PrEP with medical advice and monitoring. This is especially the case if you want to stop PrEP. Event-based dosing (EBD) is not suitable if you have hepatitis B or if you do not know your hepatitis B status. EBD is when you take PrEP around the time of sex.
Hepatitis A and B vaccination is recommended for gay, bisexual, and men who have sex with men and people who inject drugs.
Hepatitis A and B
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 monitoring of your kidneys.
How often this happens can depend on:
- your age
- your medical history
- any medicines you take
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.
