HIV patients have their blood drawn mainly for HIV viral load and CD4+ T lymphocyte count, as these two indicators are very important for HIV patients. If the HIV viral load is below the lower limit of the test, the patient’s treatment is very effective and the current antiviral drugs can suppress the virus completely. If the virus remains at a certain level for a long time and taking medications does not cause the virus to drop, the patient may need to change medications for treatment. The CD4+ T-lymphocyte count reflects the patient’s immune function. By checking the CD4+ T-lymphocyte count, the probability of a possible infection can be assessed and the need for prophylactic drug treatment can be determined.