2.12 Viral load on and off treatment
Viral load before starting HIV treatment (ART)
Before you start ART, the CD4 count is more important than viral load.
Even though everyone should now use ART, the CD4 count show how urgent it is to start.
Viral load tests are still useful. They help estimate when someone might have become HIV positive. But this is still just a best-guess based on other factors including history of risk and possible seroconversion symptoms..
One exception is when viral load is higher than 100,000 copies/mL. This is because some HIV drugs can only be used at lower levels. This include starting ART with oral rilpivirine, also in Odefsey and Eviplera.
The combination of raltegravir plus FTC/tenofovir (TD or TAF) should not be used if baseline viral load is >100,000 copies/mL. Dual therapy with doluteravir/lamivudine needs to have baseline viral load less than 500,000 copies/mL.
Viral load when on treatment
On ART, viral load is more important than the CD4 count.
This is because your CD4 count is probably already increasing.
Your viral load when on ART shows how well treatment is working.
If viral load gets to less than 50 copies/mL then ART is likely to last for many years. When viral load is this low, resistance is rare. It usually only develops if you are late or miss taking your medication.
But if viral load stays above 50, even if still below 500, drug resistance can still develop.
Sometimes though, low-level detectable viral load doesn’t mean that ART is not working. Sometimes, even with perfect adherence, viral load can remain detectable. This is only a recent research finding and there is currently no test to find out whether detectable viral load is a problem or not. (See: HTB report from Halvas et al.).
How fast does viral load drop on ART
Viral load usually goes down by at least 90% (1 log) within the first few days of treatment.
It usually drops by 99% (2 logs) within the first month. Most people reach undetectable (less than 50 copies/mL) within three months.
How quickly viral load becomes undetectable depends on three main factors.
- How high viral load is when you start ART.
- The drugs in your ART. Integrase inhibitors reduce viral load more quickly than other types of HIV drugs.
- How good you are are taking all your meds.
If viral load does not drop by at least 90% (1 log) within 4 weeks,your doctor needs ot find out why this is so low.
How often to use viral load tests?
How often viral load should be tested varies in different guidelines.
UK and US guidelines recommend a viral load test when diagnosed. Then about four weeks after starting ART, and every 1-2 months until viral load is undetectable.
If the CD4 count is very low (less than 350 or 200 cells/mm3), tests might be every month.
Once viral load is undetectable on stable ART, tests are recommended every 6 to 12 months.
What if you do not have access to a viral load test?
If you do not have access to a viral load test, your doctor will manage you based either on CD4 tests or on clinical symptoms.
Not having a viral load result should not stop you from beginning ART.
Some countries do not have routine access to viral load tests, but ART still works very well.
Last updated: 1 January 2023.