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) quickly reduce viral load. 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.

Information on this website is provided by treatment advocates and offered as a guide only. Decisions about your treatment should always be taken in consultation with your doctor.


  1. Lisa Thorley

    Hi Val,

    How are you coping with your diagnoses? Are you able to get any support?

    Your viral load is already quit low. Therefore, unless you have problems with your treatment it should be undetectable for when you give birth. If not within the next few months.

    Due to you being pregnant you may find the following helpful:


  2. Val

    I tested HIV positive on Feb 27 2017. My viral load was 2200, while my CD4 is 280 . I’m 5 months pregnant and started my medication in March. My question is, can my viral load go down to zero before I give birth? I’m due for 30th August 2017.

  3. Lisa Thorley

    Hi Sani,

    If your doctor is already aware that you may be resistant to your treatment it is irresponsible of them to wait until August to recheck your viral load. Therefore, please go back to the clinic and ask them to retest your viral load.

    As for having a resistance test done, could you try another clinic or hospital? I’m asking because its important that you find out if you’re resistant to your meds or not. If you are you will need to change, and sooner rather than later.

  4. Sani

    Thank you for your reply Lisa. My doctor said maybe I’m resistant to the drug I am on and that I’m due for another viral load test in August and if its still high or doesn’t drop she will place me on another drug. She said that the drug resistant test is supposed to be conducted before I’m placed on another drug but they don’t have the facilities to do the test because the test is quite expensive. I’m worried about waiting too long because I dont want to fall sick or my condition to get worse. And I’m in Abuja Nigeria. Thanks

  5. Lisa Thorley

    Hi Sani,

    You can email me at lisa.thorley@i-base.org.uk.

    For support groups in Nigeria, I’ll need to know where you are in Nigeria.

    Now with regards to your viral load, this by now should be undetectable. Therefore, this is something that you should talk to your doctor about. You taking Atripla at 10pm or 10.30pm won’t impact this, and your doctor should know this.

    Yes there has been a slight drop with your CD4, try not to worry about this. This is because CD4s can and do change all of the the time. For example in the morning is could be 522, then even 570 in the afternoon. Your CD4 is great.

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