ImmunologyInfectious Disease

CD4 Count

Normal Range
500-1500 cells/mm³
Sample Type
Whole Blood (EDTA)
Fasting
No
Unit
cells/mm³

Function

The CD4 count is a test that measures the number of CD4 T-lymphocytes (helper T cells) in the blood. These cells are the 'conductors' of the immune system, signaling other immune cells to fight off infections. This test is the primary marker used to assess the health of the immune system, particularly in patients with Human Immunodeficiency Virus (HIV).

Why it is Ordered

  • HIV Management: To determine the stage of HIV infection and the risk of opportunistic infections.
  • Treatment Monitoring: To evaluate the effectiveness of Antiretroviral Therapy (ART).
  • Organ Transplant: To monitor immune suppression in transplant recipients.
  • Immunodeficiency Evaluation: To investigate chronic, recurrent infections in non-HIV patients.

Associated Conditions

  • HIV/AIDS: HIV specifically targets and destroys CD4 cells.
  • Lymphoma: Certain cancers of the lymphatic system can lower T-cell counts.
  • Opportunistic Infections: When CD4 counts drop below 200, the body becomes susceptible to rare infections like PCP pneumonia or Toxoplasmosis.
  • Sepsis: Severe acute infections can cause a temporary drop in lymphocyte counts.

Clinical Thresholds

  • >500 cells/mm³: Generally considered a healthy immune system.
  • 200-500 cells/mm³: Indicates a weakened immune system.
  • <200 cells/mm³: Classified as AIDS (in HIV-positive individuals), indicating a high risk for life-threatening opportunistic infections.

Check Your Result

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Interactive
cells/mm³

Enter your lab result to see where you stand compared to the standard reference range.

Why Context Matters

CD4 counts are subject to significant diurnal variation; they are typically lowest in the morning and highest in the evening. Acute stress, recent surgery, or concurrent viral infections (like the flu or a cold) can cause a temporary, sharp decrease in the CD4 count that does not reflect a permanent decline in immune function. It is standard practice to base clinical decisions on a trend of multiple tests rather than a single result.

Lab ranges are statistical averages, not biological laws. "Normal" for a 20-year-old male isn't normal for a 60-year-old female.

Clinical References

Source-of-truth databases and clinical guidelines for CD4 Count:

Research & Guidelines

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DR

Medically Reviewed by Dr. Binoy Babu, MBBS

Board Certified Doctor • 10+ Years Clinical Experience

Dr. Babu is a practicing physician dedicated to empowering patients with clear, actionable medical information. He founded 2opi to bridge the gap between complex lab reports and patient understanding, ensuring everyone has access to a reliable second opinion.

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