If you have a very low count, you could get a bacterial infection. This condition is called neutropenia. Advanced HIV disease can cause neutropenia. A regular CBC does not give T-cell counts. However, the results of a CBC are needed to calculate T-cell counts, so both tests are done at the same time.
Monocytes circulate in the blood.
When monocytes settle in various tissues they are called macrophages. A high count usually means you are fighting a bacterial infection. They are involved with allergies and reactions to parasites. Sometimes, HIV disease can cause a high eosinophil count. If you have a high count, especially if you have diarrhea, gas or stomach bloating, your doctor will probably test you for parasites.