CD4+

Abnormal: 250–500 cells per cubic millimeter. It means you have a weakened immune system and may be infected with HIV.
Abnormal: 200 or fewer cells per cubic millimeter. It indicates AIDS and a high risk of life-threatening opportunistic infections.

A low CD4 count indicates that your immune system has been affected by HIV and/or the disease is progressing. At CD4 counts less than 200 cells/mm3, the immune system can no longer keep opportunistic infections in check. At low CD4 counts, a health care practitioner may recommend starting prophylactic treatment for opportunistic infections such as Pneumocystis carinii (jiroveci) pneumonia (PCP) or candidiasis (thrush). The Centers for Disease Control and Prevention (CDC) considers people who have an HIV infection and CD4 counts below 200 cells/mm3 to have AIDS (stage III HIV infection), regardless of whether they have any signs or symptoms.

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What causes a CD4 count to drop?

CD4 cells are part of the immune system. They are present in blood cells and help protect the body from disease. When HIV enters body cells, it reproduces or makes copies of itself. As it does so, it causes CD4 cells to die, leaving the body more prone to infection and disease. Typically, the more virus that’s in the body, the lower the levels of CD4 will be, the more the immune system will be compromised, and the higher the person’s risk of infection. Antiretroviral treatment suppresses the virus and gives CD4 cells a chance to recover. As a person receives treatment, they can expect CD4 levels to rise. In the first year of antiretroviral treatment, one can expect typically to see a person’s CD4 count rise by 50–150 cells/mm3. After that, there will be slower yearly increases.

What are other factors that affect CD4 count?
HIV is not the only factor affecting CD4 levels. The following can also have an impact:

- Circadian rhythms, also called the body clock, vary during the day. One result of this is that CD4 levels tend to be lower in the morning and higher as the day progresses.
- Having an infection, such as the flu, pneumonia, or hepatitis B, can cause CD4 levels to fall.
- Some treatments, such as chemotherapy or single-dose steroids can cause CD4 levels to drop. However, ongoing steroid use may increase CD4 levels.

Other factors that may play a role include:

- stress
- fatigue
- nicotine or alcohol use
- pregnancy

For this reason, there may be some variation in CD4 levels, even if a person’s health status has not changed. Also, the CD4 level will not affect how a person feels. Some people have low CD4 levels and function well, while others experience complications despite having higher levels.

Notes: 

Importantly, any single CD4 test result may differ from the last one even though your health status has not changed. Usually, a healthcare practitioner will take several CD4 test results into account rather than a single value and will evaluate the pattern of CD4 results over time.

The CD4 count tends to be lower in the morning and higher in the evening. Acute illnesses, such as pneumonia, influenza, or herpes simplex virus infection, can cause the CD4 count to decline temporarily. Cancer chemotherapy can dramatically lower the CD4 count.

The CD4 count does not always reflect how someone with HIV disease feels and functions. For example, some people with higher counts are ill and have frequent complications, and some people with lower CD4 counts have few medical complications and function well.