HIV is detectable by a blood test. The test tells you if you are infected with the Human Immunodeficiency Virus (HIV) by looking for antibodies. HIV antibodies are your immune systems response to HIV in your blood. Antibodies are proteins produced by the immune system to fight a specific germ.

Other tests are used when people already know they are infected with HIV. A viral load test is used to measure how many cells are being infected and killed by the HIV virus and is usually done when an individual is diagnosed with HIV infection and at regular intervals following diagnoses. A CD4 cell count measures the number of CD4 cells in a sample of blood. It is used by health care providers to determine when to begin, interrupt, or halt-anti-HIV therapy, when to give preventive treatment for opportunistic infections, and to measure an individual’s response to treatment. The lower the CD4 count, the higher the risk of an individual developing an opportunistic infection. The healthy range for a CD4 cell count is: 500-1500.