Treatment as prevention
When someone with HIV takes effective treatment it reduces their viral load to undetectable levels. This means the level of HIV virus in the blood is so low that it can't be detected by a test.
Having an undetectable viral load for 6 months or more means it isn't possible to pass the virus on during sex. This is called undetectable=untransmittable (U=U), which can also be referred to as "treatment as prevention".
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A condom is the most effective form of protection against HIV and other STIs. It can be used for vaginal and anal sex, and for oral sex performed on men.
HIV can be passed on before ejaculation through pre-come and vaginal secretions, and from the anus.
It's very important condoms are put on before any sexual contact occurs between the penis, vagina, mouth or anus.
Lubricant, or lube, is often used to enhance sexual pleasure and safety by adding moisture to either the vagina or anus during sex.
Lubricant can make sex safer by reducing the risk of vaginal or anal tears caused by dryness or friction, and can also prevent a condom tearing.
Only water-based lubricant (such as K-Y Jelly) rather than an oil-based lubricant (such as Vaseline or massage and baby oil) should be used with condoms.
Oil-based lubricants weaken the latex in condoms and can cause them to break or tear.
HIV prevention medication
If you're HIV negative, you may be able to take pre-exposure prophylaxis (PrEP) medication to reduce your risk of getting the virus.
PrEP is available for some people who are at high risk of HIV infection – for example, those whose partner is HIV positive.
It's available as a tablet, and is to be taken before you have sex and are exposed to HIV. You'll be able to get the medication from sexual health clinics across England.
Read more about the PrEP trial to prevent against HIV infection.
Screening for HIV in pregnancy
All pregnant women are offered a blood test to check if they have HIV as part of routine antenatal screening.
If untreated, HIV can be passed from a pregnant woman to her baby during pregnancy, birth or breastfeeding.
Read more about screening for HIV during pregnancy.