Blood tests before and during PrEP: HIV, kidney and hepatitis B explained
Why you need an HIV test, a kidney function test and a hepatitis B test before starting PrEP, how often they are repeated, and what the results mean.
PrEP is very safe for most people, but it is a prescription medicine, and a few blood tests make sure it is right for you. Malaysia’s national PrEP guideline, like guidelines worldwide, asks for these tests before you start and regularly while you take it.
Before starting PrEP: a recent HIV test (taken close to the day you start), a kidney function test (creatinine) and a hepatitis B test. Doctors usually add syphilis and hepatitis C. While on PrEP: an HIV test every 3 months, kidney function at least once a year, and sexual health checks (syphilis at least every 6 months, or every 3 months for men who have sex with men and trans women).
1. HIV test: why it comes first
PrEP contains two HIV medicines. That is enough to prevent HIV, but not enough to treat it. If someone who already has HIV takes PrEP, the virus can become resistant to these medicines, which makes future treatment harder. That is why a negative HIV test is required before starting, and why it is repeated every 3 months.
Tell the doctor if you had a possible exposure in the last few weeks, or flu-like symptoms (fever, sore throat, rash, swollen glands). Very recent HIV infection may not show up on a test yet, and the doctor may want to repeat it.
2. Kidney function test
Tenofovir is cleared from the body by the kidneys. In a small number of people it can affect kidney function, so a blood test (creatinine, used to estimate creatinine clearance) is done before starting. Malaysia’s guideline says the TDF/FTC PrEP tablet should not be started if creatinine clearance is below 60 mL/min.
The test is repeated at least once a year, or more often if you are 50 or older, have diabetes or high blood pressure, or regularly take anti-inflammatory painkillers such as ibuprofen or diclofenac.
3. Hepatitis B test
Tenofovir and emtricitabine also act against the hepatitis B virus. If you have hepatitis B, PrEP can still be used, but stopping it suddenly can cause the hepatitis to flare up, so the doctor needs to know. If you are not immune, you may be offered the hepatitis B vaccine.
Other tests your doctor may suggest
- Syphilis: at the start and at least every 6 months (every 3 months for men who have sex with men and trans women), because PrEP doesn’t prevent other sexually transmitted infections.
- Hepatitis C: at the start, and yearly for people at higher risk.
- Gonorrhoea and chlamydia: every 3 months for men who have sex with men and trans women, otherwise depending on your risk.
- Pregnancy test: when relevant. PrEP can be used in pregnancy, but your doctor will discuss it with you.
Where to get the tests
You can have them at a government clinic, a private lab, or at CAREPLUS Clinic in Kepong. If you already have kidney and hepatitis B results from the last 12 months, you can use them to order PrEP online: attach them at checkout. Your HIV test needs to be recent, and our doctor will ask for a new one if it isn’t. If you don’t have results, just place your order: our doctor will contact you for a free consultation and tell you what you need.
What if a result is abnormal?
- HIV test reactive: you won’t be given PrEP. The doctor will arrange a confirmatory test and, if HIV is confirmed, treatment, which today lets people with HIV live long, healthy lives.
- Kidney function low: the doctor may repeat the test, review your other medicines, or advise against PrEP.
- Hepatitis B positive: PrEP may still be suitable, with closer follow-up. Never stop it without speaking to the doctor.
Read the full guide to PrEP in Malaysia.
7. Questions people ask
Can I start PrEP without a blood test?
No. A negative HIV test is required, and Malaysia’s PrEP guideline also asks for kidney and hepatitis B tests. If you don’t have recent results, our doctor offers a free consultation and will tell you which tests you need.
How recent do my test results need to be?
Kidney and hepatitis B results from the last 12 months are usually fine. The HIV test needs to be recent, close to the day you start PrEP, because an older negative result can’t rule out a new infection. Our doctor will ask for a new HIV test if needed.
How often are the tests repeated on PrEP?
An HIV test every 3 months, kidney function at least once a year (more often if you are 50 or older or at higher risk), and syphilis at least every 6 months (every 3 months, with gonorrhoea and chlamydia checks, for men who have sex with men and trans women).
Can I take PrEP if I have hepatitis B?
Often yes, but your doctor needs to know, because stopping PrEP suddenly can make hepatitis B flare up. You will be followed up more closely.
