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. Lisa Thorley

    Hi Raman,

    Its not possible for me to say what caused the allergic reaction, that is if this was in fact an allergic reaction. You being on anti hive medication won’t be the issue as your ARVs won’t have a negative interaction with these. Neither do you antibiotics that you were given interact with your ARVS. This is something that you’ll need to discuss with a doctor.

  2. Raman

    Started ARVs (Tivicay + Descovy) on Monday, 25th February 2019. No side effects until Saturday. On Saturday night, drank 4 pints of chilled beer. On Sunday and Monday, ran fever, sore throat and a stiff neck. Elevated levels of C reactive protein and ESR made my GP put me on an antibiotic (azithromycin). Started antibiotic course of Tuesday, even though I was already starting to get better. On Tuesday night developed an ulcer on lip, and on Wednesday night developed angioedema of lips despite purposely skipping the antibiotic dose on Wednesday ( I have previously been intolerant to other antibiotics like amoxicillin). The fever had completely subsided by Wednesday morning.
    By the look of it, what may have caused the allergic reaction, the antibiotic, or the ARVs I’d been taking? Could it also be IRIS? The only other medication I’m on are antihistamines for hives that I have regularly, like Levocetirizine and Fexofenadine.
    Baseline CD4 – 240
    Baseline VL – 37000 copies

    Thank you very much!

  3. Lisa Thorley

    Hi Khukhu,

    The advice that your doctor has given you is correct. If your viral load is increasing like this, this means that your medication isn’t working like it needs to. This is why you’ll need toc change. There’s info about this here: http://i-base.info/guides/changing

    Its still very possible that you can have a negative child, but changing medication is important. There’s info about pregnancy here: http://i-base.info/guides/pregnancy

  4. Khukhu

    Hi, i started taking meds (Odimune) on the last year and my Viral load was 3380copies and my CD4 was 280. I’m taking my medicine well but my viral load is getting higher than before… On the 9th of January it was 4780 copies and I took another blood test now it’s worse its 5740copies and Cd4 is 211 and I’m pregnant . So my doctor says that I’m in danger I have to switch to another second regimen because I’ll end up infecting my baby.

  5. Roy Trevelion

    Hi Khukhu,

    What does your doctor say about it? Did they tell your why your ARVs were not working well?

    What are the ARVs you’ve been taking, and what ARVs will they switch to? Please let us know more info. Do you have access to your CD4 count and your viral load results?

  6. Khukhu

    I took Arvs for 10 months and Viral load is keeping on increasing and now they are switching me to a second line ART… So will my viral load decreases.. M so worried

  7. Roy Trevelion

    Hi Agnes,

    HIV affects your CD4 cells. These cells are a type of white blood cell.

    But unfortunately we are not doctors at i-Base. So it’s important that you go for the colonoscopy and other tests and ask for any necessary treatment.

    It’s good that you’re taking your ARVs, what meds are they?

    Does your HIV doctor talk to the others who are doing these tests for the bleeding. Can you ask them to work together on your treatment?


Your e-mail address will not be published. Required fields are marked *