Q and A


Does viral load need to be undetectable for six months for U=U?


I know that U=U means having my undetectable viral load protect my partner. My question is how long to I have to wait with an undetectable viral load before relying on this. 

Some web sites say to wait for six months or to have my viral load confirmed. As I only get one viral load test a year, do I really have to wait this long?



Thanks – this question will be important for lots of people. In practice, just getting undetectable viral load is likely to be enough, but this is based on limited direct data.

So you are also right that different web sites have different information. This is also the case with different HIV treatment guidelines. Currently, UK guidelines are still cautious and recommend waiting six months after viral load is undetectable in blood. However, this is based on little data and so might easily change in the future.

As background, before the results from the PARTNER studies, doctors and researchers were very cautious. When people thought there might still be a small risk, they recommended having an undetectable viral load for six months before relying on U=U. The six month wait was included for people to join the PARTNER study.

This wait period was to make sure viral load was confirmed to be undetectable, using a second viral load test. Also, this additional time was thought to make sure viral load was also undetectable in genital fluids as well as in blood.

However, modern HIV drugs seem pretty good at reducing viral load in sexual fluids at the same time as HIV is reduced in blood. [1, 2] Even though several studies have reported that viral load is sometimes detectable in genital fluid when undetectable in blood [3, 4, 5], there were still zero transmissions in the PARTNER studies (where viral load was only measured in blood). [6, 7]

This means that guidelines are likely at some point to become more relaxed about waiting for six months. As doctors get more confident about U=U, guidelines are likely to reduce this to three months or one month in the future, or for one undetectable result in blood to be enough.

If this happens, it will be based on a practical interpretation of different types of data. It will not come from direct studies like PARTNER.

Currently there is very little evidence to support that waiting for six months is likely to be important.

Some doctors already think that waiting for a month might be fine as a compromise (until guidelines are reviewed and hopefully updated). Others think that once you are undetectable in blood, this will be enough.


  1. Imaz A et l. HIV-1-RNA decay and dolutegravir concentrations in semen of patients starting a first antiretroviral regimen. JID 214(10); 1512–1519. (15 November 2016).
  2. Gianella S et al. Genital HIV-1 hhedding with dolutegravir (DTG) plus lamivudine (3TC) dual therapy. JAIDS. DOI: 10.1097/QAI.0000000000001863.
  3. Lambert-Niclot S et al. Detection of HIV-1 RNA in seminal plasma samples from treated patients with undetectable HIV-1 RNA in blood plasma on a 2002-2011 survey. AIDS 26:971-975. (15 May 2012)
  4. Ferraretto X et al. Timing of intermittent seminal HIV-1 RNA shedding in patients with undetectable plasma viral load under combination antiretroviral therapy. PLoS One (3 March 2014). DOI: 10.1371/journal.pone.0088922.
  5. Cu-Uvin S et al. Genital tract HIV-1 RNA shedding among women with below detectable plasma viral load. AIDS 24(16):2489-97. (3 October 2010).
  6. i-Base report of PARTNER 1 study.
  7. i-Base report of PARTNER 1 study.


  1. Lisa Thorley

    Hi Asa,

    Your viral load is undetectable, this means that your HIV is under control. You’re doing really well. This is what it means to be undetectable: http://i-base.info/u-equals-u/

  2. Asa

    Hi,ASA MY vl is less than 20 i hope im ok


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