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 a study from 2006 in people using efavirenz-based combinations. It reports an average viral load reduction of 1.9 logs after only 10 days on treatment.

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

This answer was updated in January 2016 from a question first posted on 15 September 2012.


  1. Roy Trevelion

    Hi Nomsa,

    I’m sorry to hear this is giving you stress. But it’s good that you’re taking your ARVs in time and everyday. Did the nurses mean that HIV was not detected, but now HIV is detected again?

    Please can you talk to the nurses and ask them to check your viral load again?

    Sometimes the viral load result comes back detectable. That means over 50 copies m/L. But it can be just a blip. A blip is when viral load goes above 50 copies/mL for a short time and then drops back down.

    Please let us know what ARVs you’re taking. And if you have access to your viral load results, please tell us those results too.

  2. Nomsa

    Hi I’m HIV positive in 2016 nurses said the virus was not active but now when they took a blood test the results said the virus is active again, this is worrying me I never make a mistake of not taking my ARV I took my ARV in time and everyday so this is giving me a stress

  3. Roy Trevelion

    Hi Gilly,

    It’s good that you started HIV treatment (ART) immediately. Starting ART is the best way to look after your health. It’s the only way to stop progress to other HIV symptoms and infections.

    Please see this guide to Introduction to ART.

  4. gilly

    Hi I just got tested but had no symptoms save for flu I suppose. Ithe came out positive and I immediately started treatment. I’d like to know if this means it won’t progress to other symptoms? Really worried. (I intend on staying on treatment)

    Thank you

  5. Roy Trevelion

    Hi Tebogo,

    It’s great that you started HIV treatment (ART) right away. Being on ART is the best way to protect your health. And this can also reduce the risk of HIV to your baby to close to zero.

    The aim of ART is to get your viral load to undetectable as soon as possible and before it’s time to give birth. Please see this link to HIV pregnancy and women’s health.

    If you have an undetectable viral load you cannot transmit HIV, even if you don’t use condoms. So ART can protect your partner too. Please see this link to Undetectable = Untransmittable (U=U).

  6. Tebogo

    Hi i found out that i was hiv positive at 12 weeks of pregnancy i started treatment right away problem is sometimes my partner and dont use protection and he is not on treatment i am now 23 weeks will my baby be affected?

  7. Roy Trevelion

    Hi Bello,

    Are you back on treatment now? What meds are you taking? And if you have access to your CD4 count and viral load, please let us know.


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