HIV: Undetectable = Untransmittable (U=U)

The science behind Undetectable = Untransmittable, its benefits in addressing HIV, and how to spread the word.

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Understanding the science

Strong scientific evidence tells us that HIV is not passed on through sex when:

These very low amounts of HIV are undetectable by many HIV tests. That's why it's called Undetectable = Untransmittable (U=U).

Research and evidence

Serodiscordant couples are those where one partner is living with HIV and the other partner is not. Studies on these couples show that HIV is not passed on through sex when the partner living with HIV is on treatment and the amount of HIV in their blood remains very low.

Consistent medication keeps HIV levels low

Keeping HIV levels low doesn't mean a person is cured of HIV. However, people who take their HIV treatment consistently can live a long healthy life.

U=U doesn't apply to non-sexual activities

Keeping HIV levels low may also reduce the risk of passing it through non-sexual activities like:

  • sharing drug use equipment
  • pregnancy, breastfeeding or chestfeeding

However, there's not yet enough evidence to say that there is no risk of HIV being passed in these ways. HIV cannot be passed through touching, kissing or hugging.

HIV levels do not determine value

Some people living with HIV may not be able to keep their levels low due to circumstances beyond their control, like lack of access to medication. No one should be shamed for not being on treatment or for having any amount of virus in their blood.

There are other highly effective ways to prevent HIV from being passed during sex, like:

  • condoms
  • pre-exposure prophylaxis (PrEP)
  • post-exposure prophylaxis (PEP)

Everyone living with HIV has the right to full and healthy social and sexual lives.

Prevention methods

When to use condoms

Condoms can help prevent pregnancy and other sexually transmitted infections like:

  • syphilis
  • chlamydia
  • gonorrhea

They can also be useful if a person doesn't know their partner's sexual history.

If a person keeps their levels low, they won't pass HIV to their partner or partners. This means they don't need to use condoms and medicines like PrEP and PEP during sex.


Share the U=U message

Knowing about U=U helps challenge HIV stigma and discrimination. Most importantly, people living with HIV who know about U=U are also more likely to report better mental, physical and sexual health. This life-changing science has transformed what it means to live and love with HIV across the globe.

Knowing about U=U:

These benefits all support the global goal of ending HIV and AIDS as a public health concern by 2030.

Listen to what U=U means to those living with HIV

In this episode of the Healthy Canadians podcast, host Megan Beahen, speaks with Adrian Betts, Executive Director of the AIDS Committee of Durham Region, and Claudette Cardinal, Peer Indigenous Research Associate of the BC Centre for Excellence in HIV/AIDS, about how the life-changing science on Undetectable = Untransmittable has transformed what it means to live and love with HIV.

Listen on


Learn more and help raise awareness.

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For health professionals

Health professionals have an important role to play in improving awareness of U=U. It's essential that they fully understand and communicate this message with all their patients to:

Prioritizing a person-centered approach and patient-led care can help start the conversation. This may look like asking patients:

This way, health professionals can find out how to best support their patients' needs.

Antiretroviral treatment

Antiretroviral treatment (ART) is used to treat HIV. When a person living with HIV takes it every day, it lowers the amount of HIV in the blood. This treatment:

The amount of HIV in the blood is called the viral load. When HIV treatment lowers the viral load to less than 200 copies of virus per milliliter of blood, it is called viral suppression. To confirm that a person is virally suppressed, their viral load is usually measured regularly (every 4 to 6 months) as part of clinical care.

Scientific studies show that when someone's viral load is suppressed, the amount of HIV in blood and sexual fluids is so low that it is not passed on to others through sex. HIV is untransmittable when someone maintains viral suppression.

An undetectable viral load means that the amount of HIV in a person's blood is so low that it does not show up in standard tests. As HIV tests become more advanced, the exact amount of HIV that is "undetectable" continues to change. However, any test result that shows an amount less than 200 copies of virus per milliliter of blood means that HIV is untransmittable.

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