Immature Granulocytes (Percent)
The share of your white blood cells that are young, not-yet-mature granulocytes. Clinicians read it with the rest of your CBC.
AI-verified against cited sources. Awaiting expert reviewAlso called IG%LOINC 71695-1
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What it is
Granulocytes are white blood cells that help fight infection. They normally stay in the bone marrow until they mature. Immature granulocytes (IG) are earlier stages. Their names are metamyelocytes and myelocytes and, at some labs, promyelocytes. Some blood counters count them and report them as a percent of all your white blood cells. Bands (a slightly later stage) and blasts are counted separately. Not every lab reports IG.
Why it matters
A higher IG percent is a clue that your bone marrow is releasing young cells. This often happens during an infection, inflammation, an injury or when taking certain medicines. It is also seen in pregnancy. Labcorp notes that a raised IG percent is not, by itself, a reliable predictor of disease. Clinicians read it with your white blood cell count, your neutrophils and how you feel.
If it’s high
A high IG percent means more of your white cells are young forms than is usual for your lab. Many things can raise it. Often the cause is passing, such as an infection, pregnancy or a medicine. It can also be linked to blood or bone marrow conditions, so a result that stays high is worth a talk with your clinician.
Common causes
- Infection, including common bacterial infections
- Pregnancy, especially in the later months
- Inflammation, injury, surgery or other tissue damage
- Steroid medicines, chemotherapy and growth-factor injections (cytokine therapy)
- Other stresses on the body, such as red blood cells breaking down (hemolysis) or seizures
- Being a newborn, when levels are higher in the first days and months of life
- Blood or bone marrow conditions, such as myeloproliferative neoplasms or leukemia
What can help
- Ask your clinician to read IG together with your white blood cell count, your neutrophils and the absolute IG count
- If you were sick, injured or pregnant when the blood was drawn, ask whether repeating the CBC later makes sense
- Tell your clinician about any steroid, chemotherapy or growth-factor medicines you take
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.
For adults: 0–0.9 %. Source: ARUP Laboratories, Oregon Health & Science University (OHSU Lab Services), Archives of Pathology & Laboratory Medicine, Clinical Laboratory, Medicine (Baltimore), Labcorp, MHCC Laboratory (test catalog powered by Mayo Clinic Laboratories).
What can affect your result
- Age: levels are higher in newborns and infants than in older children and adults
- Pregnancy, especially the later months
- Infection, inflammation, injury or surgery
- Medicines such as steroids, chemotherapy and growth-factor injections
- The lab's analyzer: not every lab reports IG, and each lab uses its own range
- Not every lab reports IG, and each analyzer defines and counts it a little differently, so ranges from one lab do not transfer to another.
- Infection, injury, pregnancy, steroid medicines, chemotherapy and growth-factor injections can raise IG, so recent illness or treatment can change a result.
- A difficult blood draw or a refrigerated sample can trap white cells in small clots and throw off automated counts.
Reflects what your bone marrow is releasing around the time of the draw, so it can change from one test to the next.
When to talk to a clinician
A slightly high IG percent on its own rarely needs urgent attention. Contact your clinician promptly if it is raised and you also have a fever or chills, a racing heart, or you feel very unwell. Call 911 or your local emergency number for chest pain, trouble breathing, confusion or fainting.
Questions you could ask
- Which results on my differential matter most for me?
- Is my absolute immature granulocyte count also raised?
- Could an infection, pregnancy or a medicine I take explain this?
- Should we repeat the CBC after I have recovered, and when?
Questions people ask
Does a high immature granulocyte percent mean I have an infection?
Not necessarily. Infection is one thing that can raise it, but so can pregnancy, injury, steroid medicines and other causes. A normal IG percent also does not rule out an infection. Your clinician reads it with your symptoms and the rest of your CBC.
Why does my report say 'Not Estab.' for immature granulocytes?
Some labs, including Labcorp, do not set a range for the IG percent and print 'Not Estab.' (not established). Percentages shift whenever another cell type changes. Labcorp does print a range for the absolute IG count, so that number can be easier to judge.
What is the difference between immature granulocytes and bands?
Both are young white cells. IG are the earlier stages and bands are a slightly later stage. Labs usually count them on separate lines, and the IG count does not include bands or blasts.
Show the science and sources
For clinicians and researchers
IG are the early granulocyte forms (metamyelocytes, myelocytes and, in some definitions, promyelocytes) counted by some automated hematology analyzers as a share of leukocytes. Bands and blasts are excluded. Labcorp's CBC page defines IG as metamyelocytes and myelocytes with promyelocytes and blasts reported separately, while a footnote on its sample report includes promyelocytes, so definitions differ between sites. Intervals are method-specific. ARUP lists 0.2 to 0.9% for ages 18 and over, OHSU 0.0 to 1.0% from age 1 month, one health-system catalog (MHCC) 0 to 5%, and Labcorp prints 'Not Estab.' for the percent. A Brazilian study of 115 healthy donors reported 0 to 0.63%, an indirect study of 25,431 Sysmex XN-1000 records reported 0.10 to 0.60%, and an outpatient study of more than 2,400 samples recommended upper limits of 0.30% (age 10 and under) and 0.90% (over 10) with no difference between the sexes. In a 2003 study of 171 patients on a Sysmex XE-2100, an IG above 3% was a very specific but not sensitive predictor of sepsis, so it is not a screening test for infection.
LOINC 71695-1 (primary), 38518-7. Specimen: whole-blood.
Sources
- CBC with Platelet Count and Automated Differential (test 0040003), hotline effective March 1, 2021, ARUP Laboratories (2021)
- CBC with Differential, Oregon Health & Science University (OHSU Lab Services)
- Complete Blood Count (CBC) With Differential, Reflex to Peripheral Smear Review (test 005009), Labcorp
- CBC With Differential/Platelet, sample patient report (test 005009), Labcorp
- Pediatric Testing Reference Ranges, Labcorp
- Complete Blood Count (CBC) with Automated Differential (test code CBCD), MHCC Laboratory (test catalog powered by Mayo Clinic Laboratories)
- CBC (includes Differential and Platelets) (test code 6399), Quest Diagnostics
- Age-dependent reference ranges for automated assessment of immature granulocytes and clinical significance in an outpatient setting, Archives of Pathology & Laboratory Medicine (2011)
- Definition of Reference Range for the Immature Granulocytes Parameter Provided by a Hematology Analyzer, Clinical Laboratory (2021)
- Local reference intervals for MacroR, MicroR, IG% and IG# on Sysmex XN-1000: A retrospective indirect LIS-based study, Medicine (Baltimore) (2026)
- Immature granulocyte measurement using the Sysmex XE-2100. Relationship to infection and sepsis, American Journal of Clinical Pathology (2003)
- Immature granulocyte detection by the SE-9000 haematology analyser during pregnancy, Clinical and Laboratory Haematology (2003)
AI-verified against cited sources. Awaiting expert review. Last reviewed 2026-10-03. How we build and check these pages.