Undetectable viral load (U=U)

U=U is short for Undetectable = Untransmittable

U=U means that a person living with HIV who is on treatment and has an undetectable viral load cannot pass HIV on through sex.

Key things to know

If you have an undetectable viral load, you cannot pass on HIV to other people through sex.
  • HIV treatment works by reducing the amount of HIV in your body.
  • You are undetectable when the amount of HIV in your blood is so low that it can no longer be detected.
  • Only your doctor can confirm that you have an undetectable viral load.
  • Continuing your treatment and maintaining an undetectable viral load is key in preventing HIV transmission through sex.

If you need help understanding HIV treatment and viral load, you can get in touch with us for advice and support.

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What is a viral load?

Viral load is the term used to describe the amount of HIV in your blood. When you first get HIV, the virus rapidly multiplies (makes copies of itself) and spreads throughout your body.

When viral load is measured, the test results describe the number of HIV copies in a millilitre of blood. Low viral load means that your HIV treatment is working. An undetectable viral load means that there is very little of HIV in your blood and tests are no longer able to detect it. This means you can’t pass it on to your partners through sex.


How will I know that I am undetectable?

Becoming undetectable can take up to 6 months after you start HIV treatment. Your doctor will perform blood tests and let you know when you’re undetectable.

Your viral load will be measured again at least 6 months after the first undetectable reading. To maintain an undetectable viral load, you must continue taking your HIV medication and visit your specialist HIV clinic regularly. Blood tests will be done regularly to make sure you’re still undetectable.


Why is having an undetectable viral load important?

Some of the many benefits of having an undetectable viral load include:

  • it shows that the HIV treatment is working for you,
  • it allows your immune system to repair itself so you are less prone to illnesses,
  • it prevents further damage to your immune system,
  • an undetectable viral load means that you will not pass HIV on during sex, and
  • having an undetectable viral load means that you can have a healthy pregnancy and reduce the risk of HIV being passed on to your baby.


Other important information

U=U only prevents HIV from being passed on through sex. It doesn’t prevent transmission by other routes, such as sharing injecting equipment, but it is likely to reduce the risk.

You won’t transmit HIV through sex provided that you have had an undetectable viral load for 6 months and are absent of any sexually transmitted infections (STIs), such as gonorrhoeasyphilis and chlamydia.

U=U is only about HIV and does not prevent the transmission of hepatitis C or other STIs. Condoms and lube remains the best protection against a range of STIs.

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If you are living with HIV and need support understanding a new diagnosis, treatment or navigating life with HIV, we are here to help. Get in touch with us by filling out our contact form.

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