Q and A


How quickly does viral load drop on treatment?

I’ve been trying to understand on average, the daily rate of decrease in viral load following initial treatment.

I’m guessing that this changes over time and varies from case to case according to the chosen treatment, CD4 count and viral load level and possibly other factors.

However, supposing that the viral load is around 100,000, the CD4 count is around 400 and the treatment used is Atripla, could anyone please let me know the expected % decrease of viral load level per day at least within the 1st month of treatment?

Thank you for the help.


All HIV combinations (ART) starts working from the first dose.

Viral load is usually reduced by 90% (also referred to as 1 log) within the first few days. It then continues to fall but not as quickly (see below) until it becomes undetectable.

A log is a number mulitplied to the power of 10. So with a viral load of 100,000 copies/mL, a 1-log reduction would bring your viral load down to 10,000 copies/mL and a 3-log reduction would reduce it to 100 copies/mL. (See this factsheet).

You are right that individual factors will lead to difference rates of viral load reductions. These include:

  • How high your viral load was when you start ART.
  • The medicines in the combination (integrase inhibitors casuing the fastest drops).
  • The drug levels of this meds (related to adherence and how they absorb and processes drugs).
  • Good adherence – not missing doses.

UK and US guidelines recommend that your viral load should be undetectable within three months. However, many people achieve this within the first month, especailly if they are using an integrase inhibitor.

Some people take longer, especially if their viral load is very high when they start treatment.

Lots of studies have reported detailed early responses ART, including for efavirenz-based combinations like Atripla.

This decline is often referred to as having three main phases.

The first phase is very rapid – referred to in some studies as being the first few days and in others as within the first two weeks. This is where the actively infected CD4 cells are targeted. CD4 cells infected with HIV only live for a few days and when you start treatment this virus and these cells are quickly reduced.

This results in a viral load drop of perhaps 99% (2 logs) within two weeks.

The second phase, out to the first month is slower, as it is working on cells that live longer. This can easily reduce viral by another 90% (another 1 log reduction). In people with very high viral loads when they start treatment, this second phase may continue for longer until viral load becomes undetectable.

Some researchers also talk about a third phase decline which occurs even more slowly and gradually once your viral load is undetectable.

This relates to a reduction in the levels of infected CD4 cells that are latent (or resting). This pool of cells only slowly decreases over time.

This link is to an early study describing the two-phase viral load reductions.

This answer was updated in July 2020 from a question first posted on 15 September 2012.


  1. Lisa Thorley

    Hi C,

    A person’s viral load should become undetectable within 1-3 months of starting medication. In some instances it might be quicker or even longer. This is why it’s important to have your viral load monitored when you start taking ARVs. If you’ve only been back on meds it’s very possible that your viral load was still detectable.

    The risk that you’ve described is quite low. However, if the risk was within the last 72hrs your partner could start PEP. At some point they should test.

  2. C

    Hello. My VL had 7,000 copies before retaking my ATV. When I restarted, I’ve been properly taking my meds five days straight. No missed doses. I’m scared because on the fifth day I ended up having sex. It was a heated moment. I did use protection with her. However, the condom broke and when I noticed during that moment I had a small friction. It didn’t hurt nor was it bleeding at all. I’m scared and worried now, that I may have transmitted HIV. How soon will I notice a drop in my VL that will decrease the chances of transmission before having an UNDETECTABLE VL?

  3. Lisa Thorley

    Hi Tshengie,

    If your viral load has rebounded it’s very likely that you’ll need to change combination, please see here for more info: https://i-base.info/guides/changing You’ll need to discuss this with your doctor.

  4. Tshengie

    I started taking Arvs in 2012 but now they’re saying my viral load is too high what can I do to to boost my immune system because I am not feeling well got fever and cough

  5. Lisa Thorley

    Hi Otzy,

    Shortness of breath and coughing aren’t side effects of ARVs. If you’re feeling unwell please see a doctor.

  6. Otzy


    I started taking ARV Last month 25 may 2021 and i was suffering from shortness of breath and coughing i have maybe 3 weeks now but am still suffering from shortness of breath and coughing

    how long does it work form such symptoms when take ARV ?

  7. Lisa Thorley

    Hi Luxolo,

    When someone starts taking ARVs their viral load should become undetectable within 1-3 months of starting medication. To know for sure what your viral load is, you’re going to need to have it tested. Due to being pregnant, you should be having your viral load checked.

    For more info on pregnancy, please see here: https://i-base.info/guides/pregnancy


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