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What does undetectable mean?

  • A person living with HIV is considered to have an ‘undetectable’ viral load when antiretroviral treatment has brought the level of virus in their body to such low levels that blood tests cannot detect it.
  • There is no risk of passing on HIV if your doctor has confirmed that you are undetectable (or virally suppressed), you continue taking your treatment and attend regular viral load monitoring appointments. Undetectable = Untransmittable.
  • Being undetectable isn’t a constant state and if you stop taking your medication then your viral load will go back up again.

You might have noticed that ‘undetectable’ has become a bit of a buzzword, and there’s a reason why it’s becoming a popular term among people living with HIV.

As the name suggests, an undetectable viral load occurs in people living with HIV when the virus exists in such small quantities that it can’t be detected by standard blood tests.

Graphic showing U = U

Many people living with HIV can achieve an undetectable viral load by adhering to antiretroviral treatment over a period of at least six months. Evidence has shown that as long as you continue to have your viral load monitored by a health professional to confirm that you are undetectable, then there is zero risk of you transmitting HIV to others and your health will not be affected by HIV. Undetectable = Untransmittable.

Here we look at what it means to be undetectable if you are living with HIV, or if you are HIV-negative but are having sex with someone who is undetectable…

Why it’s important to have your viral load checked

‘Viral load’ refers to the amount of virus in the blood. It is measured by a simple blood test which also shows how well antiretroviral treatment is working at protecting your immune system from other potential illnesses.

An ‘undetectable’ diagnosis means that the level of HIV in your body is so low (under 40 copies/ml) that it is non-infectious to other people. You might also hear healthcare workers talking about ‘viral suppression’ (where HIV levels are under 200 copies/ml) - if you have had either of these diagnoses then there is zero risk of you passing on HIV.

It usually takes the body a while to adjust to new medicines, and the same goes for HIV treatment. Simply being on treatment doesn’t automatically mean that you’re undetectable and it’s very common for viral loads to fluctuate, particularly early on after starting a new treatment regime.

You might look and feel perfectly healthy, but simply feeling fine isn’t a good indicator of what your viral load looks like. The only way to know that you are undetectable is through regular viral load monitoring.

It’s recommended that you should be taking treatment for at least six months, and then have your viral load monitored every 2-4 months by a healthcare professional to know that you are undetectable.

It’s important to remember that, even if you have an undetectable viral load, HIV is still present in your body. This means that if you stop taking treatment then your viral load can increase – affecting your long-term health and making HIV transmittable again.

Can everyone living with HIV achieve an undetectable viral load?

Not everyone living with HIV can achieve an undetectable viral load and this is usually down to factors out of someone’s control.

For some people, it might be tricky to find a treatment regime that agrees with them. While in some places, viral load testing may not always be readily available.

If this is the case for you, it’s essential that you still take your medication exactly as prescribed and that you keep regular appointments with your doctor. While you may not be ‘undetectable’, you can still remain healthy.

If you’re not sure about your viral load status then there are still other ways to reduce the risk of HIV transmission among your sexual partners. Your partners may want to consider taking pre-exposure prophylaxis (PrEP) to keep themselves HIV-negative. Using condoms will prevent both HIV transmission and other sexually transmitted infections.

If you aren’t able to get your viral load monitored regularly, it’s important not to assume that you are undetectable.

I’m ‘undetectable’, what does this mean for me? 

Of course, if you are able to remain undetectable under the correct treatment and monitoring pattern, the great news is that you don’t have to worry about passing HIV onto your sexual partners!

Being undetectable also means that your body is in good health and that your immune system is working well at defending itself from daily germs. Maintaining your treatment and monitoring routine is key to remaining undetectable, but is also a good way to ensure that you stay healthy.

Sharing your diagnosis can be a tricky conversation to have, but you might want to explain what ‘undetectable’ means to your sexual partners as it can help to put their mind at ease as well as yours.

Having this discussion may impact your decision to stop using condoms as your main form of protection during sex.

However, it’s still a good idea to speak to your doctor or health professional before changing your protection routine. You should also keep in mind that while being undetectable stops the transmission of HIV it doesn’t stop unwanted pregnancies or the transmission of other sexually transmitted infections (STIs).

What does ‘undetectable’ mean if you are HIV negative? 

If you're HIV-negative and your current sexual partner is living with HIV and has an undetectable viral load, then there is no risk of sexual transmission of HIV.

You and your partner might decide to stop using condoms, but you should never feel pressured into changing your existing protection routine if it’s one that works for you. You may actually find it reassuring to take control over your own sexual health and wellbeing.

Even if your partner is undetectable, condoms are still the only form of protection that also prevent other STIs and unwanted pregnancies. You may also want to look into PrEP as an extra precaution against HIV. 

Whatever decision you make about protection, it is still best to regularly test for HIV to check that your status remains negative.

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Photo credit: © Photos are used for illustrative purposes. They do not imply any health status or behaviour on the part of the people in the photo.

Last full review: 
28 September 2017
Next full review: 
27 September 2020
Last updated:
27 February 2020
Last full review:
28 September 2017
Next full review:
27 September 2020