A white blood cell count measures the total number of white blood cells in a blood sample. A high result is called leukocytosis; a low result is called leukopenia. Neither result names a cause by itself. A WBC differential separates the major cell types, and absolute counts—especially the absolute neutrophil count (ANC)—can make the pattern more useful. Follow-up depends on symptoms, medications, recent illness, prior results, the laboratory’s reference interval, and whether red blood cells or platelets are also abnormal. A CBC can support an evaluation, but it cannot identify a particular infection or reliably label an illness as bacterial or viral on its own.1,2
White blood cells, also called leukocytes, are produced mainly in bone marrow and participate in immune defense, inflammation, allergic responses, and tissue repair. A total WBC count reports how many white blood cells are present in a specified volume of blood. It does not show how well each cell functions and does not measure “immune strength.”
A CBC reports the WBC count alongside red blood cell and platelet measurements. A CBC with differential also separates the five major types of white blood cells. Because a change in one subtype can alter the total—and can make another subtype’s percentage look lower or higher—clinicians often look beyond percentages to the absolute number of each cell type.1,2
| Result | What it reports | How to use it | Important limitation |
|---|---|---|---|
| Total WBC count | All white blood cells combined | Shows whether the total is within, above, or below that laboratory’s reference interval | Does not show which subtype changed or why |
| Differential percentage | The proportion of each major WBC type | Shows the distribution of cell types | A percentage can shift because another cell type changed |
| Absolute subtype count | The measured or calculated number of a specific WBC type | Clarifies whether that cell type is truly high or low | Still requires clinical context and the report’s interval |
| ANC | The absolute number of circulating neutrophils | Helps assess neutropenia and infection risk in context | One value cannot establish the cause or predict every infection |
The differential reports neutrophils, lymphocytes, monocytes, eosinophils, and basophils. Laboratories may report percentages, absolute counts, or both. The ANC is usually reported directly or derived from the total WBC count and neutrophil components. Use the value and units printed on your report; do not compare a result with a range from a different laboratory or with a value reported in different units.A white blood cell count shows a pattern. The differential and absolute neutrophil count add context, while symptoms, history, trends, and other tests help determine what the pattern means
| Cell type | General role | Patterns that may prompt follow-up |
|---|---|---|
| Neutrophils | Rapid response to infection, inflammation, and tissue injury | High or low absolute neutrophil counts; immature forms; change from baseline |
| Lymphocytes | Adaptive immune responses and immune memory | Persistent high or low absolute lymphocyte counts; atypical cells; symptoms |
| Monocytes | Removal of microbes and damaged cells; regulation of inflammation | Persistent change, especially with other abnormal counts or symptoms |
| Eosinophils | Participation in allergic disease and responses to some parasites | Degree and persistence of elevation, travel or exposure history, medicines, and symptoms |
| Basophils | Release of inflammatory mediators in allergic and immune responses | A persistent absolute increase, particularly when other blood-cell results are abnormal |
These associations are not one-to-one rules. For example, neutrophils may rise with infection, inflammation, corticosteroid exposure, tissue injury, or physiologic stress. A lymphocyte pattern cannot prove that an illness is viral. The differential narrows questions; it does not provide a stand-alone diagnosis.
Neutropenia means the ANC is below the applicable reference or clinical threshold. The practical significance depends on how low it is, how long it has been low, the person’s baseline, symptoms, medical conditions, medicines, and current treatment. A falling ANC during chemotherapy is a different situation from a stable, mildly lower baseline in a person who feels well. International guidance therefore emphasizes history, repeat measurements when appropriate, medication review, other blood-cell lines, and targeted evaluation—not an isolated number alone.4
Some people with the Duffy-null phenotype have a lower baseline ANC without increased infection risk. The American Society of Hematology calls this Duffy-null associated neutrophil count, or DANC. Duffy status is a biological trait; race and ethnicity are not reliable substitutes. A clinician may consider this context when an otherwise well person has a stable lower ANC, but DANC should not be assumed solely from appearance, race, or ancestry—and it should not be used to dismiss new symptoms or a changing blood count.5
A low total WBC count can result from fewer cells being produced, faster destruction or use of cells, redistribution between blood and tissues, or a lower healthy baseline. The differential helps show whether the decrease is mainly in neutrophils, lymphocytes, or another subtype.
One low result may be transient or may reflect normal biological and laboratory variation. A repeat test can sometimes confirm whether the change persists, but timing should match the clinical situation. A person with fever, significant symptoms, active chemotherapy, or a critical laboratory alert should not wait for a routine repeat test.
A high total WBC count can occur when the body releases or produces more white cells. The most useful next question is often: which cell type is high, and what else is happening?
High does not automatically mean dangerous, and low does not automatically mean harmless. Magnitude, persistence, symptoms, subtype, and the rest of the CBC determine the urgency of follow-up.3
A CBC can show a blood-cell pattern that is compatible with infection, but it cannot confirm that an infection is present, identify a pathogen, locate the infection, or reliably distinguish a bacterial illness from a viral one by itself. Some people with infection have a normal total WBC count. Some people without infection have a high or low count because of medicine, inflammation, treatment, pregnancy, smoking, physiologic stress, or a blood disorder.
| They can help | They cannot do alone |
|---|---|
| Show whether the total count and cell subtypes are above or below the reporting laboratory’s interval | Name the bacterium, virus, fungus, or parasite causing an illness |
| Reveal whether red blood cells or platelets are also abnormal | Determine where an infection is located |
| Provide a baseline and show trends during illness or treatment | Prove that an illness is bacterial or viral |
| Help a clinician decide whether more targeted evaluation is appropriate | Replace symptoms, examination, cultures, molecular tests, imaging, or clinical judgment |
For a broader explanation of choosing tests based on the suspected organism and body site, see Infectious Disease Testing.
The sequence below is educational and does not replace individualized care. The safest next step depends on symptoms and clinical context.
For help reading flags, units, reference intervals, and trends, use the How to Read and Understand Lab Results guide.
Choose the narrowest test that answers the question, while recognizing when the broader CBC context matters. The linked Ulta Lab Tests pages below were verified during this update. Review each current product page for specimen and preparation instructions before ordering.
| Test | What it measures | When it may fit | What it cannot determine alone |
|---|---|---|---|
| White Blood Cell Count (Total) | Total WBC count | A focused total-count check when other CBC components are not needed | Which WBC subtype changed or why |
| White Blood Cell Count with Differential | Total WBC count plus the major WBC types | Clarifying whether a total-count change is driven by neutrophils, lymphocytes, monocytes, eosinophils, or basophils | A specific infection, immune disorder, or blood disorder |
| Complete Blood Count with Differential and Platelets | WBCs and differential, red blood cells and indices, hemoglobin, hematocrit, and platelets | A broader blood-cell baseline or follow-up when more than the total WBC count matters | The cause of an abnormal result |
| Vitamin B12 Test | Blood vitamin B12 concentration | Targeted evaluation when history, diet, absorption risk, symptoms, or CBC pattern raises concern for deficiency | Whether B12 explains an isolated WBC result without the rest of the clinical picture |
| Folate Serum Test | Serum folate concentration | Targeted evaluation of suspected folate deficiency | The cause of leukopenia by itself |
| Copper Test | Blood copper concentration | Selected cases with compatible history or blood-cell and neurologic findings, including malabsorption or excess zinc exposure | Whether a supplement is appropriate or safe |
A total WBC count is narrower than a differential. A CBC with differential is broader because it also shows red-cell and platelet patterns. That broader view can be important when more than one blood-cell line is affected. If the concern is a specific infection, select testing based on symptoms, timing, body site, and exposure—not from the WBC pattern alone.
There is no universal, evidence-based way to increase a WBC count with a particular food, supplement, exercise plan, sleep schedule, or stress-reduction technique. Those measures may support general health, but they should not be presented as treatments for leukopenia or neutropenia.
The right response is cause-directed. That may mean monitoring a transient change, treating an identified condition, correcting a confirmed deficiency, or having a prescriber reassess a medicine. In selected medical settings, clinicians may use prescription treatment to stimulate neutrophil production. That decision depends on the cause, expected benefit, and risks; it is not a self-treatment strategy.
Do not start high-dose vitamin or mineral supplements simply to change a WBC result. Too much of a nutrient can be harmful, and supplementation can obscure the underlying question. Copper is a good example: deficiency can affect blood counts, but excess copper can be toxic, and high zinc intake can contribute to copper deficiency. Test and treat in context.7
Direct-access testing can provide useful data, but it does not replace urgent care or medical evaluation. Learn more in Direct Access Lab Testing: What to Know.
Do not use an online article or a repeat lab order to delay care when symptoms are concerning.
No. Infection is one possible cause, but inflammation, corticosteroids and other medicines, smoking, pregnancy, tissue injury, physiologic stress, and some blood or bone marrow disorders can also raise the count. The differential, absolute counts, symptoms, and trend help determine what to investigate.
No. A person can have an infection with a WBC count inside the reporting laboratory’s reference interval. Diagnosis may depend on symptoms, examination, exposure, the body site involved, and targeted testing. A normal CBC should not override concerning symptoms.
Not reliably. Certain differential patterns may be more common in some illnesses, but there is substantial overlap. A CBC cannot identify a pathogen. Clinicians choose cultures, molecular tests, antigen tests, or other evaluations based on the clinical question.
The WBC count includes all white blood cell types. The ANC focuses on neutrophils. When neutrophils are low, the ANC is often more useful than the total count for assessing infection risk, but it still needs context such as symptoms, treatment, duration, and baseline.
No. Some results are temporary, mild, or normal for the individual. Risk depends on which cell type is low, how low and persistent it is, symptoms, medicines, medical conditions, and whether other blood cells are affected. Fever or illness with neutropenia deserves prompt attention.
No single food or supplement is proven to safely raise WBCs across all causes. If testing confirms a deficiency that affects blood-cell production, targeted treatment may be appropriate under clinical guidance. Taking high doses without evidence of deficiency can cause harm and may delay the correct evaluation.
Yes. Physiologic stress, recent intense activity, smoking, corticosteroids, chemotherapy, and other medicines can affect the total count or differential. Report these factors when interpreting an unexpected result. Never stop a prescribed medicine without speaking with the prescriber.
Sometimes. Repeating the test can show whether a result was transient or persistent, but the appropriate timing depends on the value, symptoms, recent illness, treatment, and other CBC findings. Critical values, chemotherapy fever, or significant symptoms need immediate guidance rather than routine retesting.
DANC is a lower baseline ANC associated with the Duffy-null phenotype and is not linked to increased infection risk. It should be considered using biological and clinical context, not assumed from race or ethnicity. A new change or symptoms still require appropriate evaluation.
The result alone does not define every emergency. Fever during chemotherapy is an emergency at 100.4°F (38°C) or higher. Fever or rapidly worsening infection symptoms with known or suspected neutropenia, a critical-value alert, severe breathing difficulty, chest pain, fainting, or confusion requires immediate guidance or emergency care.
A white blood cell count is most useful as part of a pattern. Start with the total count, then review the differential, absolute subtype counts, ANC, other CBC components, symptoms, medicines, and trend. Do not use the result to self-diagnose a specific infection or to choose supplements. Use targeted testing and clinical follow-up when the pattern calls for it, and treat chemotherapy fever or serious symptoms as urgent.
This article is for educational purposes and does not diagnose, treat, or replace medical advice. Ulta Lab Tests is a direct-to-consumer laboratory testing service. When you purchase a test through links in this article, Ulta Lab Tests may receive revenue from that purchase. Test availability and requirements can change; review the current product page before ordering. Seek urgent medical care when symptoms or your treatment team’s instructions indicate it.
Update note: This article replaced advice about “increasing” white blood cells with cause-based interpretation; clarified that CBC patterns do not identify a specific infection; added WBC differential, absolute-count, ANC, and DANC guidance; and consolidated relevant material from the retired article about red and white blood cell counts.
Originally published: December 6, 2023 | Substantively updated: September 3, 2026
| Test | Use in this article |
|---|---|
| Complete Blood Count with Differential and Platelets | Preferred broader evaluation when red blood cells, white blood cells, differential results, and platelets all matter |
| White Blood Cell Count Test with Differential | Focused evaluation of the total WBC count and the five major WBC types |
| White Blood Cell Count Test | Narrow total-count measurement when differential and other CBC components are not required |
| Test | Appropriate role |
|---|---|
| Vitamin B12 Test | Targeted evaluation when history, diet, absorption risk, symptoms, or the broader CBC pattern raises concern |
| Folate Serum Test | Targeted evaluation when folate deficiency is clinically plausible |
| Copper Test | Selected cases involving compatible blood-cell findings, malabsorption, gastrointestinal surgery, neurologic findings, or excess zinc exposure |
The Complete Blood Count with Differential and Platelets may also be used for repeat or monitoring purposes when appropriate. The repeat interval should depend on symptoms, treatment, severity, trends, and professional guidance—not a universal schedule.
| Rank | Related Health Area | Why it belongs |
|---|
| 1 | CBC, Anemia, Iron, and Blood Cell Testing | Primary pillar covering CBC components and related blood-cell patterns |
| 2 | Infectious Disease Testing | Explains pathogen-specific testing and why a CBC cannot identify an infection by itself |
| 3 | Inflammation and Autoimmune Blood Tests | Provides context when inflammation or autoimmune disease is part of the clinical question |
| 4 | Vitamin and Nutrient Deficiency Tests | Supports selective investigation of B12, folate, and copper status |
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