Before you start PrEP

PrEP should not be used if you are HIV positive. 

You may not need PrEP if you are:

  • using condoms consistently and intend to continue doing so
  • only having 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 can’t be detected by standard blood tests. It means the level of HIV in your body is so low, it can’t be passed on. This needs to be monitored regularly by a healthcare professional.

Tests you need before you start PrEP

If you decide to start taking PrEP, there are a few tests that you will need first.

HIV test

You must have a 4th generation HIV test before or as you start PrEP. A blood sample will be taken, usually from your arm, and sent to a laboratory. This test has a window period of around 45 days.

The window period is the time between when you may have been exposed to HIV, and the point when the test will give an accurate result. During the window period, you can be infected with HIV but still have a negative HIV test.

If there is a chance that you have been exposed to HIV in the last 45 days, tell your healthcare provider. You may need more blood tests and a repeat HIV test 45 days (or around 6 weeks) after starting PrEP. This is to make sure that an early infection is not missed.

If you have had a recent HIV risk and have developed flu-like symptoms, this may be a sign of HIV seroconversion. This 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 provider will explain this to you.

If you are starting PrEP after PEP, it is best to start immediately after you finish the course of PEP. There is no need to delay starting PrEP after PEP. You should have a 4th generation HIV blood test around the time you finish PEP/start PrEP. You should have another HIV blood test 4 to 6 weeks after starting PrEP.

Sometimes a rapid HIV test is done in addition to the laboratory HIV test. It may be possible to start PrEP on the day of your first PrEP appointment. This will be discussed with you in greater detail by your healthcare provider.

Read more about HIV testing

Hepatitis B

It is essential to have a test for hepatitis B because PrEP medicines are active against both HIV and hepatitis B. Taking PrEP if you have undiagnosed Hepatitis B could 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, especially if you want to stop. Event based dosing (EBD) is not suitable if you have hepatitis B or if you don’t know your hepatitis B status.

Hepatitis A and B vaccination is recommended for gay, bisexual, and men who have sex with men and people who inject drugs.

Kidney function

Kidney monitoring involves a blood test for creatinine, and sometimes a urine test for protein. These should ideally be done just before or on the day you start PrEP.

Sexually transmitted infections (STIs)

You should have STI testing, which includes testing for:

  • syphilis
  • chlamydia
  • gonorrhoea
  • hepatitis C

HPV vaccination is recommended for gay, bisexual, and men who have sex with men up to 45 years of age. HPV vaccination protects against genital warts and HPV-associated cancers.

Pregnancy test

People who can get pregnant will need to have a pregnancy test before starting PrEP. This may be reviewed again during follow-up as needed.

People who are pregnant can take PrEP following discussion with a doctor specialising in genitourinary medicine or infectious diseases.