Segmented neutrophils (segs) on a blood test: normal percentage and what high or low means
Segmented neutrophils (Segs) · Complete blood count (CBC) with differential · reported in percent of white blood cells (segs %, neutrophils relative); absolute count in ×10³/µL (K/µL) or cells/µL
Segmented neutrophils, usually shortened to segs (and on older reports called polys or PMNs), are fully mature neutrophils, the white cells that engulf and kill bacteria and fungi and make up the largest share of your white blood cell count. The name refers to the nucleus, which in a mature neutrophil is pinched into two to five connected lobes; the slightly younger band neutrophil has a smooth, curved nucleus and is counted separately when a technologist reads the slide. On a CBC with differential, segs are reported as a percentage of all white cells (often labelled "neutrophils relative" or "neutrophils %") and most labs also calculate the absolute number. In adults, segs are normally about 40 to 60 percent of white cells, and the absolute neutrophil count is about 1.5 to 8.0 ×10³/µL.
The percentage is the number most people are flagged on, and it is the less useful of the two. Because it is a share of the total, segs can be "high" simply because lymphocytes are low, or "low" because lymphocytes are high, with a perfectly normal number of actual neutrophils. The absolute count (white cell count multiplied by the percentage) is what clinicians act on, which is why a high or low segs percentage is always read alongside the WBC and the absolute neutrophil count.
High segs almost always mean a response to infection, inflammation, stress or medication, with bacterial infection and corticosteroids at the top of the list. Low segs most often mean a viral infection, a drug effect, or the common inherited Duffy-null trait that gives many people of African ancestry a naturally lower count with no increased infection risk. The thresholds that matter clinically are absolute: below 1,500 per µL is neutropenia, below 500 is severe and raises infection risk substantially.
Segs at a glance
- What it is: mature neutrophils with a lobed nucleus, reported as a percentage of white cells (segs, neutrophils relative) and as an absolute count.
- Normal (adults): about 40–60% segs on a manual differential, or 40–75% "neutrophils" on an automated count that includes bands; absolute 1.5–8.0 ×10³/µL. Bands normally under 5–6%. Labs differ.
- Children under about 5 have lower neutrophil percentages (often 20–45%) because lymphocytes dominate; newborns run high for the first days.
- High segs: bacterial infection, inflammation, stress, exercise, pregnancy, smoking, obesity, corticosteroids, surgery or injury; rarely a bone marrow disorder. Above 10–12% bands with high segs is a left shift suggesting acute bacterial infection.
- Low segs: viral infections, medications (chemotherapy, methotrexate, clozapine, some antibiotics and antithyroid drugs), Duffy-null trait, B12/folate/copper deficiency, autoimmune disease, an enlarged spleen or a marrow disorder.
- Next step: always convert to the absolute count; a flagged percentage with a normal absolute neutrophil count usually needs nothing more than a repeat.
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What Segs measures
Neutrophils are made in the bone marrow over about two weeks and spend only 6 to 10 hours in the circulation before moving into tissues, so the blood count is a snapshot of production, release and demand. About half of the neutrophils in blood vessels are not counted at any moment because they are stuck to vessel walls (the marginated pool); exercise, adrenaline, stress and corticosteroids shift them into the flowing blood within minutes, which is why segs rise with no infection at all.
On a manual differential, a technologist classifies 100 white cells on a stained film and reports each type as a percentage, separating segmented neutrophils from bands by the shape of the nucleus. Automated analyzers classify tens of thousands of cells but cannot reliably tell a band from a seg, so they report a single "neutrophils" figure that includes both; a lab will add a manual band count or an immature granulocyte count when a left shift matters. This is why your report may say "segs" on one occasion and "neutrophils relative" or "neut %" on another: they are the same cells counted two ways.
The absolute count is the percentage multiplied by the total white cell count. A segs of 75 percent with a WBC of 5.0 ×10³/µL is 3.75 ×10³/µL of neutrophils, which is normal; the same 75 percent with a WBC of 18 is 13.5, which is neutrophilia. Equally, segs of 35 percent with a WBC of 8.0 is a normal 2.8, while 35 percent of a WBC of 3.0 is 1.05, which is mild neutropenia. Reference ranges for the percentage exist, but the absolute number is what the thresholds for neutropenia and neutrophilia are based on.
Normal range for Segs
Reference ranges vary between labs and by age, sex and pregnancy. Use the range printed on your own report.
| Group | Typical range (percent of white blood cells (segs %, neutrophils relative); absolute count in ×10³/µL (K/µL) or cells/µL) | Notes |
|---|---|---|
| Adults, segs on manual differential | 40–60% (some labs 35–65%) | Bands reported separately, normally 0–5%. Labs differ; use the printed range. |
| Adults, automated neutrophils % | 40–75% | Includes bands. Commonly printed as neutrophils relative, neut % or NE%. |
| Adults, absolute neutrophils | 1.5–8.0 ×10³/µL (some labs 1.8–7.7 or 2.0–7.0) | This is the number thresholds are based on; see the absolute neutrophil count page. |
| Duffy-null phenotype (common in people of African ancestry) | Absolute 1.0–1.5 ×10³/µL can be normal | Lower counts are a normal inherited variant with no added infection risk. |
| Children, about 1–5 years | 20–45% (absolute 1.5–8.5 ×10³/µL) | Lymphocytes outnumber neutrophils until roughly age 4 to 6. |
| Newborns, first week | 50–70% in the first day, falling quickly | Absolute counts up to 26 ×10³/µL at birth are normal and settle within days. |
| Pregnancy, third trimester | Up to about 70–80% | Absolute counts up to 10–15 ×10³/µL are seen near term and during labor. |
| Neutropenia thresholds (absolute) | Below 1.5 mild; below 1.0 moderate; below 0.5 severe ×10³/µL | Infection risk rises below 1.0 and sharply below 0.5. |
| Neutrophilia (absolute) | Above about 7.7–8.0 ×10³/µL | Most often reactive; above 30 ×10³/µL with immature cells needs haematology review. |
High segmented neutrophils (neutrophilia)
A high segs percentage first needs the absolute count. If the WBC is normal and only the percentage is high, the usual explanation is that lymphocytes are relatively low (for example on steroids, after a stressful event, or with age), and the finding is not neutrophilia at all. If the absolute count is above about 7.7 to 8.0 ×10³/µL, that is neutrophilia, and the commonest causes are infection, particularly bacterial, and inflammation of any kind. Bacterial infections typically produce counts of 10 to 25 ×10³/µL with a left shift (more bands and immature granulocytes).
The second large group has nothing to do with infection. Corticosteroids (prednisone, dexamethasone, even a steroid injection) raise neutrophils within hours by releasing marginated cells and marrow reserves, commonly to 10 to 20 ×10³/µL, and keep them up for as long as the drug is taken. Physical or emotional stress, pain, vigorous exercise, seizures, surgery, heart attack, burns and trauma all do the same through adrenaline and cortisol. Smoking, obesity, pregnancy and lithium each produce a persistent mild neutrophilia of 8 to 12 ×10³/µL.
Persistent neutrophilia with no reactive cause is uncommon and raises the question of a myeloproliferative neoplasm, most importantly chronic myeloid leukemia, which usually presents with a WBC above 30 to 50 ×10³/µL, immature granulocytes, basophilia and an enlarged spleen. The pattern, rather than the number alone, is what prompts a blood film and BCR-ABL test.
Common causes
Bacterial infection
Pneumonia, urinary and kidney infections, cellulitis, abscess, appendicitis and bloodstream infection drive neutrophils to 10 to 25 ×10³/µL with a left shift; severe sepsis can paradoxically lower the count as neutrophils are consumed.
Inflammation and tissue injury
Surgery, trauma, burns, heart attack, pancreatitis, gout flares, rheumatoid arthritis and inflammatory bowel disease all raise segs through cytokine-driven marrow release.
Corticosteroids
Prednisone 20 to 40 mg typically raises the neutrophil count by 2 to 5 ×10³/µL within 4 to 6 hours, mainly by demargination and delayed exit from the blood; the lymphocyte percentage falls at the same time, which exaggerates the segs percentage.
Physical and emotional stress, exercise, pain
Adrenaline shifts marginated neutrophils into the circulating pool within minutes, producing a transient rise of 50 to 100 percent that resolves within an hour or two of rest.
Smoking
Smokers run neutrophil counts about 1 to 2 ×10³/µL higher than non-smokers in proportion to cigarettes per day; the count falls over one to five years after quitting.
Obesity and metabolic syndrome
Adipose-tissue cytokines sustain a mild chronic neutrophilia, often 7 to 10 ×10³/µL; weight loss lowers it.
Pregnancy and labor
Neutrophil counts rise progressively, reaching 10 to 15 ×10³/µL near term and higher during labor, then normalize within a few weeks of delivery.
Medications other than steroids
Lithium, G-CSF (filgrastim), beta-agonists such as albuterol, and epinephrine raise neutrophils; recovery after chemotherapy can produce a rebound overshoot.
Splenectomy
Removal of the spleen leads to a persistent mild neutrophilia and thrombocytosis because the spleen normally holds a share of circulating cells.
Myeloproliferative neoplasms
Chronic myeloid leukemia, polycythemia vera, essential thrombocythemia and primary myelofibrosis cause sustained neutrophilia, often with basophilia, immature granulocytes, abnormal platelets or an enlarged spleen.
Symptoms that can go with it
- Often none when the rise is from stress, exercise, smoking, obesity or steroids
- Fever, chills, sweats and a localised source (cough with colored sputum, painful urination, red hot skin, abdominal pain) with bacterial infection
- Pain, swelling and redness at a surgical site or injured area
- Joint pain and swelling with gout or inflammatory arthritis
- Fatigue, night sweats, weight loss, fullness under the left ribs or easy bruising, which point toward a marrow disorder
- Fast heart rate, breathlessness or confusion with sepsis, which needs emergency care
Low segmented neutrophils (neutropenia)
A low segs percentage, like a high one, must be converted to an absolute number. A percentage of 30 to 40 with a normal white cell count usually reflects a relatively high lymphocyte count, as in young children, during a viral infection or in some people with a naturally lymphocyte-rich differential, and is not neutropenia. True neutropenia is an absolute count below 1.5 ×10³/µL (1,500 per µL); it is graded as mild (1.0 to 1.5), moderate (0.5 to 1.0) and severe (below 0.5), and infection risk rises steeply once the count is below 0.5.
In outpatients, the commonest causes are viral infections (influenza, COVID-19, Epstein-Barr virus, hepatitis, HIV) which depress the count for one to three weeks, and medications. The drug list is long and includes chemotherapy, methotrexate, azathioprine, clozapine, carbamazepine, valproate, the antithyroid drugs propylthiouracil and methimazole, sulfonamide antibiotics (including trimethoprim-sulfamethoxazole), and rituximab. Nutritional deficiencies of vitamin B12, folate and copper, autoimmune diseases (lupus, rheumatoid arthritis), an enlarged spleen and heavy alcohol use account for most of the rest.
A very common and benign finding is the Duffy-null phenotype, carried by roughly two thirds of people of West African ancestry and many people of Middle Eastern ancestry, which produces a stable absolute neutrophil count of 1.0 to 1.5 ×10³/µL (sometimes a little lower) with completely normal infection defence. In the US population survey NHANES, 4.5 percent of Black participants had a count below 1.5 compared with under 1 percent of white participants, almost entirely for this reason. A stable mild neutropenia with no infections and a normal rest-of-CBC is the typical picture and does not need a marrow test.
Common causes
Viral infections
Influenza, COVID-19, Epstein-Barr virus (mono), hepatitis A, B and C, HIV, measles, dengue and many common viruses transiently suppress neutrophil release or increase their use; counts recover within one to four weeks.
Medications
Chemotherapy and immunosuppressants are predictable; idiosyncratic neutropenia or agranulocytosis occurs with clozapine, carbamazepine, propylthiouracil, methimazole, sulfonamides, dapsone, ticlopidine and some NSAIDs, usually within the first 3 months of use.
Duffy-null (benign ethnic) neutropenia
An inherited variant of the Duffy antigen receptor leaves fewer neutrophils in the blood but normal numbers in tissues; infection risk is not increased and no treatment is needed.
Vitamin B12, folate or copper deficiency
All three impair granulocyte production; copper deficiency is seen after bariatric surgery, with excessive zinc intake, or on long-term tube feeding, and causes anemia and neutropenia together.
Autoimmune disease
Lupus, rheumatoid arthritis (particularly Felty syndrome with an enlarged spleen), Sjögren's syndrome and autoimmune neutropenia destroy neutrophils with antibodies or suppress their production.
Enlarged spleen (hypersplenism)
Cirrhosis with portal hypertension, lymphoma and storage diseases enlarge the spleen, which then traps neutrophils, platelets and red cells.
Overwhelming sepsis
In severe bacterial infection, particularly in older or frail people, neutrophils are consumed faster than the marrow can replace them, and a low count is a poor prognostic sign.
Bone marrow disorders
Aplastic anemia, myelodysplastic syndromes, acute leukemia, marrow infiltration and large granular lymphocyte leukemia reduce production; usually with anemia or low platelets as well.
Alcohol and chronic idiopathic neutropenia
Heavy drinking suppresses the marrow and lowers the count modestly; chronic idiopathic neutropenia is a diagnosis of exclusion in adults with a stable mild to moderate count and no other cause.
Cyclic and congenital neutropenias
Rare inherited disorders in which the count falls to very low levels on a roughly 21-day cycle or permanently; usually diagnosed in childhood with recurrent mouth ulcers and infections.
Symptoms that can go with it
- Often none, particularly with mild neutropenia and the Duffy-null trait
- Recurrent or unusually severe infections: mouth ulcers, gum infections, sore throats, skin abscesses, sinus infections, pneumonia
- Fever, which in someone with a count below 0.5 ×10³/µL is an emergency even with no other symptoms
- Fatigue, pallor and easy bruising if red cells and platelets are also low
- Joint pain, rashes or dry eyes and mouth with autoimmune causes
- Fullness or discomfort under the left ribs with an enlarged spleen
Read it alongside
- WBC — the percentage means nothing without it; multiply the two to get the absolute count before deciding anything.
- Absolute neutrophil count (ANC) — the number all clinical thresholds refer to; see the dedicated page for the 1,500, 1,000 and 500 cut-offs.
- Bands and immature granulocytes — a left shift (bands above 10 percent or raised IG) with high segs points to acute bacterial infection; a left shift with low segs suggests overwhelmed marrow.
- Lymphocytes — a high lymphocyte percentage is the usual reason a segs percentage looks low; viral infection, mono and childhood all raise lymphocytes.
- Hemoglobin and platelets — neutropenia with anemia or low platelets points to marrow failure, B12/folate deficiency or hypersplenism rather than a simple viral or drug effect.
- CRP — grades the inflammation driving a high count and helps judge whether a fever with a low count is a bacterial infection.
- Vitamin B12, folate and copper — checked when neutropenia is unexplained, particularly after bariatric surgery or with high zinc intake.
- ANA and rheumatoid factor — ordered when neutropenia accompanies joint pain, rashes or other autoimmune features.
What usually happens next
- Convert the percentage to an absolute count (WBC × segs ÷ 100). If the absolute neutrophil count is within 1.5 to 8.0 ×10³/µL, a flagged percentage usually needs no action beyond a repeat on a routine basis.
- For a high absolute count with an obvious reason (infection, steroids, surgery, pregnancy), repeat the CBC 4 to 6 weeks after the trigger has resolved; it should normalize. A count that stays above 10 to 12 ×10³/µL with no cause, or above 20 to 30 at any time, warrants a blood film and haematology advice.
- For a low absolute count, the first questions are about recent viral illness, new medications in the last 3 months, alcohol intake, ancestry, and any history of infections; the first tests are a repeat CBC in 2 to 4 weeks, a blood film, B12, folate and, if indicated, copper, ANA and HIV.
- If a drug is suspected, do not stop it on your own; clozapine, antithyroid drugs and chemotherapy all have specific monitoring rules, and your prescriber will decide whether to pause, reduce or continue.
- A stable mild neutropenia (1.0 to 1.5 ×10³/µL) with normal hemoglobin and platelets and no infections, especially in someone of African ancestry, can be followed with periodic counts; Duffy antigen typing can confirm the trait if there is doubt.
- Neutropenia below 1.0 ×10³/µL that persists, falls further, or comes with anemia, low platelets or an enlarged spleen is referred to haematology and may need a bone marrow examination.
Diet, lifestyle and natural levers with evidence
What can move Segs once the cause is known. Nothing here replaces finding the cause.
Stop smoking (for a high count)
Strong evidenceCross-sectional and longitudinal cohorts consistently show smokers have white cell counts about 15 to 25 percent higher than never-smokers, driven mainly by neutrophils and dose-related to cigarettes per day. After quitting, counts fall by roughly 0.5 to 1.0 ×10³/µL within the first year and approach never-smoker levels over about five years. Smoking is the single most common reason for a persistent mild neutrophilia in an otherwise healthy adult.
Weight loss where obesity is driving the count
Moderate evidenceNeutrophil counts rise with body mass index and waist size. In bariatric surgery cohorts, total white cell counts fell by about 1.0 ×10³/µL over the first year, with the neutrophil fraction accounting for most of the change, and diet-based losses of 5 to 10 percent of body weight produce smaller but measurable reductions. The effect reflects reduced adipose-tissue inflammation rather than any direct action on the marrow.
Correct vitamin B12, folate and copper deficiency (for a low count)
Moderate evidenceNeutropenia from B12 or folate deficiency resolves within 2 to 6 weeks of replacement, and copper-deficiency neutropenia (typically after bariatric surgery or with zinc supplements above 40 to 50 mg a day for months) recovers over 4 to 12 weeks once copper is replaced and excess zinc stopped. These are treatable causes that are easy to miss; replacement only helps when a deficiency is actually present.
High-dose zinc (above the 40 mg daily upper limit) taken for months can itself cause copper deficiency and neutropenia; folic acid should not be started before B12 status is known.
Reduce heavy alcohol intake (for a low count)
Moderate evidenceAlcohol is directly toxic to marrow precursors and impairs folate handling. In people drinking heavily, mild neutropenia, macrocytosis and low platelets are common and typically improve within 2 to 4 weeks of stopping or substantially reducing intake. Observational and inpatient studies show counts recovering during abstinence without other treatment.
Regular moderate exercise, but time the test
Moderate evidenceA single bout of hard exercise doubles the circulating neutrophil count for an hour or two by demargination, and a prolonged event such as a marathon causes a left shift that lasts a day. Over months, regular moderate activity lowers resting neutrophil and total white cell counts by a few percent, in step with reductions in CRP. If a count is being repeated to see whether a high result was real, avoid vigorous exercise for 24 to 48 hours beforehand.
When to see a clinician promptly
- A fever of 38 °C (100.4 °F) or higher when your absolute neutrophil count is known to be below 0.5 ×10³/µL, or below 1.0 and falling (for example during chemotherapy): this is febrile neutropenia and needs emergency assessment and antibiotics within an hour.
- A new low count while taking clozapine, methimazole, propylthiouracil, carbamazepine, methotrexate or a sulfonamide antibiotic, especially with fever, sore throat or mouth ulcers: contact the prescriber the same day.
- High segs with fever, shaking chills, a fast heart rate, fast breathing, confusion or severe pain: possible serious bacterial infection or sepsis.
- An absolute neutrophil count above 20 to 30 ×10³/µL, or any high count with immature cells, basophilia, anemia, abnormal platelets or an enlarged spleen.
- Neutropenia together with anemia or low platelets, night sweats, weight loss, bone pain or easy bruising.
- Recurrent mouth ulcers, gum infections, skin abscesses or pneumonias in someone with a persistently low count.
Frequently asked questions
What is a normal segmented neutrophil percentage?
On a manual differential, segs are normally about 40 to 60 percent of white cells in adults (some labs allow 35 to 65), with bands making up another 0 to 5 percent. Automated counts that lump bands and segs together usually give a range of 40 to 75 percent. Children under about five have lower percentages because lymphocytes predominate. The absolute neutrophil count, normally 1.5 to 8.0 ×10³/µL, is the more meaningful number.
What does it mean if segmented neutrophils are high?
If the absolute count is also high, it usually means your body is responding to a bacterial infection, inflammation, injury, surgery, physical or emotional stress, or a medication such as prednisone. Smoking, obesity and pregnancy cause milder persistent rises. If only the percentage is high and the WBC is normal, it generally means lymphocytes are relatively low and there is no real neutrophilia. Persistent unexplained neutrophilia, especially above 20 to 30 ×10³/µL, is reviewed on a blood film.
What does it mean if segmented neutrophils are low?
A low percentage with a normal white count usually reflects a high lymphocyte count (as in children, viral infections or mono) and is not a problem. A low absolute count, below 1.5 ×10³/µL, is neutropenia; the usual causes are a recent viral infection, a medication, the inherited Duffy-null trait, B12, folate or copper deficiency, autoimmune disease, an enlarged spleen or heavy alcohol use. Counts below 0.5 carry a real infection risk and need prompt attention.
What is the difference between segmented neutrophils and neutrophils relative?
They are the same cells reported in slightly different ways. "Segmented neutrophils" or "segs" is the percentage of mature neutrophils on a manual differential, where bands are counted separately. "Neutrophils relative", "neutrophils %" or "NE%" is the automated percentage, which includes bands because the analyzer cannot tell them apart. "Neutrophils absolute" or ANC is the actual number per microlitre, which is the figure that matters.
What are polys or PMNs on a blood test?
Polys (polymorphonuclear leukocytes) and PMNs are older names for segmented neutrophils, referring to the many-shaped lobed nucleus. Some reports still use them. They mean the same thing as segs, and the normal ranges are the same.
Can stress or anxiety raise segmented neutrophils?
Yes. Adrenaline released by acute stress, anxiety, pain or a difficult blood draw shifts neutrophils from the vessel walls into the circulating blood within minutes, producing a temporary rise of up to 50 to 100 percent that settles within an hour or two. Chronic stress and poor sleep are associated with mildly higher counts over time through cortisol. Stress does not produce the counts of 15 to 25 ×10³/µL seen with bacterial infection.
Is a segs of 70 or 75 percent high?
Slightly above a typical manual range of 40 to 60 percent, but within many automated ranges of up to 75 percent, and only meaningful once converted to an absolute count. With a WBC of 6.0, a segs of 75 percent gives 4.5 ×10³/µL, which is normal. It becomes relevant if the WBC is also high, if bands or immature granulocytes are raised, or if you have symptoms of infection.
What is a left shift?
A left shift means the blood contains more immature neutrophils than usual, classically bands above about 10 percent and, on modern analyzers, a raised immature granulocyte count. It indicates the marrow is releasing cells early, almost always because of a bacterial infection or significant inflammation, and it makes a high segs count more likely to be infection than stress.
References
- Blood differential test. MedlinePlus, US National Library of Medicine (2023)View source
- Neutrophilic leukocytosis. Merck Manual Professional Version (2024)
- Neutropenia. Merck Manual Professional Version (2024)
- Neutropenia (low neutrophil count). Mayo Clinic (2024)View source
- Riley LK, Rupert J. Evaluation of patients with leukocytosis. American Family Physician (2015)
- Hsieh MM, Everhart JE, Byrd-Holt DD, Tisdale JF, Rodgers GP. Prevalence of neutropenia in the U.S. population: age, sex, smoking status, and ethnic differences. Annals of Internal Medicine (2007)
- Reich D, Nalls MA, Kao WH, et al.. Reduced neutrophil count in people of African descent is due to a regulatory variant in the Duffy antigen receptor for chemokines gene. PLoS Genetics (2009)
- Honda T, Uehara T, Matsumoto G, Arai S, Sugano M. Neutrophil left shift and white blood cell count as markers of bacterial infection. Clinica Chimica Acta (2016)
- Cornbleet PJ. Clinical utility of the band count. Clinics in Laboratory Medicine (2002)
- Shoenfeld Y, Gurewich Y, Gallant LA, Pinkhas J. Prednisone-induced leukocytosis: influence of dosage, method and duration of administration on the degree of leukocytosis. American Journal of Medicine (1981)
- Higuchi T, Omata F, Tsuchihashi K, Higashioka K, Koyamada R, Okada S. Current cigarette smoking is a reversible cause of elevated white blood cell count: cross-sectional and longitudinal studies. Preventive Medicine Reports (2016)
- Dixon JB, O'Brien PE. Obesity and the white blood cell count: changes with sustained weight loss. Obesity Surgery (2006)
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