T cells can also be called CD4+ cells.
A CD4+ cell count measures the number of T cells in a cubic millilitre of blood. A measure of CD4+ cells indicates how healthy the immune system is and, in people who are HIV positive, can help to indicate how far the disease has progressed.
In a person with a healthy immune system, a CD4+ cell count generally falls between 500 and 1500. A CD4+ cell count of 200 or less in a person living with HIV may mean a higher susceptibility to opportunistic infections.
People who are HIV positive should monitor their CD4+ cell counts, and their viral load counts, regularly. Results are generally passed along and reviewed by health care professionals to support case-by-case, individualized planning in order to establish at what point an individual should consider starting or adjusting anti-HIV medications.