Taking your HIV meds as prescribed by your doctor reduces your viral load (amount of HIV in the blood) and helps keep it low. It can also help you achieve viral load suppression, which means having fewer than 200 copies of HIV per milliliter of blood. HIV meds can lower your viral load to a point where it becomes undetectable by a lab test. This is referred to as an undetectable viral load. With an undetectable viral load, HIV cannot be transmitted through sex, and it also prevents perinatal transmission and reduces the risk of transmission through breastfeeding. Taking your HIV meds as prescribed helps prevent drug resistance, which can limit your treatment options and spread drug-resistant HIV strains to others.

A viral load is the amount of HIV in the blood of someone who is HIV positive. The more the virus has replicated, the higher your viral load will be and the faster your CD4 count will decrease, increasing your risk of illness.

CD4 cells (or helper T cells) are a type of white blood cell that help fight off infection by activating your immune system to destroy viruses, bacteria, and other germs that can make you sick. A CD4 count refers to a blood test that measures the number of CD4 cells in a blood sample. This is used to check the health of your immune system if you are HIV positive. The normal range for an HIV negative person is 500 – 1,500. The goal is to keep an HIV positive person’s CD4 count as high as possible with treatment. A CD4 count below 200 indicates an AIDS diagnosis and an increased risk for opportunistic infections.

Undetectable equals untransmittable. This means that a person who achieves and maintains an undetectable viral load cannot sexually transmit HIV to others. Other sexually transmitted infections (STIs) can still be transmitted, however, so safer sex practices are recommended to prevent other STI transmission.