Viral load is a term used to describe the amount of HIV in your blood. People living with HIV have viral load tests to monitor the effectiveness of HIV treatment.
For someone on effective treatment, often this test will return results confirming an undetectable viral load. This means that the amount of HIV in the blood was so low that it could not be detected by the viral load test.
A viral blip is a reference to a short-term increase in viral load in someone who generally maintains an undetectable viral load. This means that the amount of HIV in the blood was still low, but high enough to be detected by the viral load test.
However, a viral blip is not necessarily an indication that your treatment is no longer effective, or that you are now able to pass HIV to your partner/s. For example, your viral load blip may be showing a temporary viral load of 60 copies/ml or 150 copies/ml. This is still below 200 copies/ml and research has shown that someone with a viral load below this level is unable to pass on HIV during sex.
Blips may occur due to variations in laboratory processes, or having an infection like a cold or the flu. Some studies have suggested that these blips occur due to a release of the virus from reservoirs within your body and are not an indication of ongoing virus replication.
If your viral load stays above detectable on two consecutive tests your doctor will want to discuss possible causes and whether you need to change your treatment.
For more information on viral load and how it relates to living with HIV see here.