A healthy adult or adolescent CD4 count is between 500 and 1,200 cells per cubic millimeter of blood, according to AIDS.gov. A CD4, or T-cell, is a type of white blood cell that fights infection. CD4 counts are often used to monitor the health of people with HIV.
When people have HIV, their CD4 counts assist doctors in determining when antiretroviral therapy begins, AIDS.gov explains. This treatment is a combination of medicines that helps keep the virus from spreading and killing CD4 cells. The CD4 count shows how effective the drug regimen is. If too many white blood cells are destroyed, people with HIV are vulnerable to opportunistic infections, such as lymphoma, tuberculosis, pneumonia and cervical cancer.