Learn about Viral Loads
Some guys believe it is safe to have condomless anal sex with someone whose HIV status is different to theirs if the HIV-positive guy has a low or undetectable HIV viral load.
An undetectable viral load test result indicates that test cannot find any HIV in a given blood sample. However, this does not mean that the blood is free of HIV, only that there is less than the test can measure. Detectable levels of HIV have also been discovered in the lining of the anus of HIV-positive men, even when they have undetectable HIV levels in their blood. This is rare, however these men would be able to pass on HIV while on the bottom during anal sex, even with an undetectable viral load.
For more information on viral load, click here.