Q and A


What does undetectable viral load mean?

What does undetectable viral load mean?



A viral load result tell you how much virus is in your blood.

Results are usually shown as copies per millilitre (copies/mL or c/mL).

The main aim of HIV treatment is for this to become ‘undetectable’. This does not mean that there is no HIV left in your body. It means that viral load can’t be detected using normal tests.

Viral load test have different cut-off levels. For example, some at sensitive to 500, 200, 50 or 20 copies/mL.

In the UK, monitoring HIV treatment (ART) is based on a viral load being undetectable at less than 50 copies/mL.

In term of risk of sexual transmission, undetectable refers to having a viral load that is less than 200 copies/mL

After starting ART, viral load usually becomes undetectable within 1-3 months, depending on the meds used. If you start with a high viral load it can sometimes take a little longer.

Having an undetectable viral load shows that your treatment is working.

It also means that you can no longer pass HIV on to sexual partners. The risk of this happening with an undetectable viral load is zero.

This Q&A was updated in May 2021 from an answer first published in December 2015.


  1. Simon Collins

    Hi William – I had to slight edit your comment so I hope I have the meaning right. Based on the results from the PARTNER study, i is very difficult to transmit HIV with undetectable viral load.

  2. william

    My friend is untectable 4yrs Is is possible to catch the virus from them?