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CD4+ T Helper Cells, absolute

The number of CD4+ T helper cells in a microliter of blood. These white blood cells help direct your immune response.

AI-verified against cited sources. Awaiting expert reviewAlso called CD4 abs, Th cellsLOINC 24467-3

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What it is

CD4+ T cells, also called T helper cells, are a type of lymphocyte (a white blood cell). They signal other immune cells when the body needs to fight an infection. A lab counts them with a method called flow cytometry on a blood sample. The result is the number of CD4+ T cells in each microliter of blood, often printed as cells/µL.

Why it matters

The CD4 count shows how many of these helper cells you have. Clinicians use it most to follow people who have HIV, because HIV infects and reduces CD4 cells. But it is not a test for HIV, and many other things can also move it, such as an illness or a medicine like a steroid.

If it’s low

A count below the lab's range means you have fewer CD4 cells than most healthy people. Many ordinary things can cause a temporary dip, such as a recent illness. A count that stays low can mean the immune system is less able to fight some infections, so it is worth looking into with a clinician.

Common causes

  • A recent viral or other acute illness, with counts recovering over the following weeks
  • Physical stress, such as major surgery or severe illness
  • Medicines that suppress the immune system, including corticosteroids and chemotherapy
  • Autoimmune conditions such as lupus
  • Cancer treatment or some blood cancers
  • HIV infection (the CD4 count is used to follow HIV, but it does not test for it)
  • Malnutrition
  • Rare inherited or acquired immune conditions, including idiopathic CD4 lymphocytopenia

What can help

  • Ask your clinician what might explain the result and whether a repeat test after you have recovered would help
  • Share every medicine and supplement you take, including steroids
  • If you are living with HIV, your HIV care team follows this result over time at regular visits

If it’s high

A count above the lab's range is not common and is rarely a concern on its own. Often it reflects the total number of lymphocytes in the blood being a bit higher than usual, for example after an infection.

Common causes

  • Natural variation between draws and between labs
  • Recent or ongoing infection that raised the number of lymphocytes
  • Long-term inflammatory or autoimmune conditions
  • Smoking, which is linked to somewhat higher counts
  • Having had the spleen removed
  • Rarely, a blood disorder involving T cells

What can help

  • Ask your clinician to look at it together with your complete blood count and the other lymphocyte results
  • Ask whether repeating the test in a few weeks, after any illness has passed, makes sense

Usual ranges

What labs print as the reference range, by who was tested. Ranges differ a little between labs, so the range on your own report is the one your result is judged against.

The usual range depends on age. Choose an age to see the one that applies.

Children and teens 4 ranges

See CD4 count by age and sex, with the U.S. survey numbers where they exist.

CDC HIV infection stages by CD4 count (only for people with an HIV diagnosis)

  • Stage 3 (under 200)below 200 cells/µL
  • Stage 2 (200 to 499)200 to under 500 cells/µL
  • Stage 1 (500 or more)500 and above cells/µL

What can affect your result

  • Age: ranges are higher in young children and shift a little in older adults
  • Time of day: counts vary through the day
  • Acute illness, stress, hard exercise and smoking
  • Medicines, especially corticosteroids and other immune-suppressing drugs
  • Sex: some studies find women have slightly higher counts, though most labs use one interval for both sexes
  • Pregnancy changes lymphocyte counts, so pregnancy-specific intervals exist
  • Lab and method: single-platform flow cytometry and calculated counts can differ, and each lab sets its own range
  • Samples must reach the lab fresh. ARUP accepts EDTA blood for up to 72 hours at room temperature (48 hours for heparin) and rejects refrigerated or frozen samples.
  • Some medicines can change the result. ARUP asks that medicines be listed on the request form. Corticosteroids, chemotherapy and other immune-suppressing drugs are known to lower lymphocyte counts.
  • Counts vary through the day, and an illness, hard exercise or stress can shift them for a short time. ARUP advises drawing at about the same time of day for serial results.

Any time, but try to draw at about the same time of day each time so results are easier to compare. Can shift within days during an illness or after steroid medicines, and usually recovers over weeks. Changes from treatment of a long-term condition build over months.

When to talk to a clinician

A CD4 result is not an emergency by itself. Talk with your clinician soon about a count under 200 cells/µL, which is the CDC's cutoff for stage 3 in people who have HIV. A count that low is worth looking into whatever the cause. Seek care promptly if a low count comes with repeated or unusual infections, unexplained fever or weight loss, a cough that does not go away, or trouble breathing.

Questions you could ask

  • How does my CD4 percent compare with my CD4 count?
  • How often should this be rechecked in my situation?
  • Could this be explained by a recent illness or my other lab results?
  • Should we repeat it in a few weeks?
  • What might explain this result, and could a recent illness or a medicine be part of it?
  • Should we repeat it after I have recovered, and which other tests would help?

Questions people ask

Is a CD4 count a test for HIV?

No. HIV is found with HIV-specific blood tests. A CD4 count shows how many helper T cells you have, and clinicians use it to follow people who already have HIV. It can also be low for many other reasons.

What do the numbers 500 and 200 mean?

In the CDC's staging system for HIV, 500 or more is stage 1, 200 to 499 is stage 2 and under 200 is stage 3. These stages are only used for people who already have an HIV diagnosis. They do not apply to people without HIV.

Why does my CD4 count change from test to test?

Counts move with the time of day, illness, stress, medicines and the lab method. Because of this, clinicians look at the trend over several results, and often at the CD4 percent, which tends to be steadier.

Show the science and sources

Units

  • 1 cells/µL = 1 cells/µL
  • 1 cells/µL = 0.001 ×10⁹/L
  • 1 cells/µL = 0.001 ×10³/µL

Open the CD4 count unit converter

For clinicians and researchers

CD4+ T cells are CD3+CD4+ lymphocytes, enumerated by flow cytometry on EDTA or heparin whole blood. Single-platform methods report absolute counts directly using a bead or internal quantitation standard (ARUP uses quantitative flow cytometry with an internal standard). Dual-platform methods multiply a hematology-analyzer lymphocyte count by the flow-cytometry percent and carry more variability. The count is sensitive to total white cell and lymphocyte count, diurnal variation and acute illness, while CD4 percent of lymphocytes is usually steadier, which is why percent is preferred in young children. The CDC 2014 HIV surveillance case definition stages infection by CD4 count (500 or more, 200 to 499, under 200 cells/µL) in people aged 6 and older, and the count takes precedence over the percent when both are available. These stages describe people with a confirmed HIV diagnosis and should not be applied to others. ARUP's adult interval is 430 to 1,800 cells/µL (ages 16 to 64) and 490 to 1,600 (65 and older); other labs differ.

LOINC 24467-3 (primary), 32515-9. Specimen: whole-blood.

Sources

  1. Lymphocyte Subset Panel 4 - T-Cell Subsets Percent and Absolute, Whole Blood (test 0095950), ARUP Laboratories
  2. Lymphocyte Subset Panel 2 - CD4 Percent and Absolute (test 0095885), ARUP Laboratories
  3. Revised Surveillance Case Definition for HIV Infection - United States, 2014, CDC, MMWR Recommendations and Reports 63(RR-03) (2014)
  4. CD4 Lymphocyte Count, MedlinePlus (National Library of Medicine)
  5. Reference ranges of lymphocyte subsets in healthy adults and adolescents with special mention of T cell maturation subsets in adults of South Florida, Immunobiology (University of Miami) (2014)

AI-verified against cited sources. Awaiting expert review. Last reviewed 2026-10-03. How we build and check these pages.

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