Biomarkers

High Immature Granulocytes on a CBC: What IG% and Immature Grans Abs Mean

Immature granulocytes (IG) are young white blood cells released early from the bone marrow. A high IG% or Immature Grans Abs usually reflects infection, inflammation, recent injury, pregnancy, or steroids. Learn how to read the flag, including a small one that stays high for months.

Published

September 23, 2026

Read time

12 min read

Medically reviewed by

Rhonda Collins, FNP-C

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Immature granulocytes (IG) are young white blood cells that normally finish maturing inside the bone marrow before they enter the blood. The IG count groups three early stages of the same cell line: promyelocytes, myelocytes, and metamyelocytes. [1] On a lab report they usually appear as two lines: IG% (or “Immature Granulocytes”), the share of your white blood cells that are immature, and Immature Grans (Abs) (or “IG#”), the absolute number. A high flag most often means your bone marrow is releasing cells early because the body is responding to something, such as an infection, inflammation, a recent injury, pregnancy, or a steroid medicine. [1] [2] One high result does not diagnose anything on its own.

Should you worry about high immature granulocytes?

Usually not, if the rest of your blood count looks ordinary and you can point to a likely trigger. A raised IG result is a sign of bone marrow activity, not a diagnosis. Three questions do most of the work:

• Was there a plausible trigger around the draw? A recent infection, an inflammatory flare, surgery or an injury, pregnancy, or a course of steroids can all explain it.
• What did the other lines on the same report do? A high IG with normal red cells, platelets, and white cell total is a different picture from a high IG next to other abnormal counts.
• Is it a single result, or has it stayed high or kept rising on repeat tests?

The pattern that deserves prompt attention is a high IG with other abnormal blood counts, a count that keeps climbing, or symptoms such as unexplained fever, weight loss, or night sweats. Those are covered in when a high IG needs follow-up below.

What IG% and Immature Grans Abs mean on your report

The two IG lines measure the same cells in different ways, and they can disagree.

• IG% is immature granulocytes as a percentage of your total white blood cell count.
• Immature Grans (Abs), also printed as IG# or “Immature Granulocytes, Absolute,” is the actual number of immature granulocytes, usually in thousands of cells per microliter (x10³/µL), which is numerically the same as x10⁹/L.

The absolute number is the percentage multiplied by the total white blood cell count, which is how every absolute line in a differential is calculated. [3] So the percentage can look high when the total white count is low, and the absolute number can look high mainly because the total white count is high. Reading both lines, together with the total, tells you which one actually moved.

Immature granulocytes are not blasts. Blasts are the earliest, least developed cells, and they are counted separately from the IG group. [4] Bands, the stage just before a mature neutrophil, are also counted separately and treated as mature on an automated IG count. [4]

What counts as a high immature granulocyte result

Compare your result with the reference interval printed beside it. That is the range your lab set for its own analyzer, and it is the one that applies to your report.

Immature granulocytes are seldom seen in the blood of healthy people. [1] Reference intervals for IG are therefore narrow, and a very small absolute value can be enough to trip the high flag. Articles that quote a single “normal range” for IG are describing one lab or one analyzer, and they will not always match the interval on your report.

A flag tells you the value is outside your lab’s interval. It does not tell you how far outside, or why. The size of the rise, the rest of the count, and whether it repeats carry more information than the flag itself.

Common causes of high immature granulocytes

A high IG result has two broad explanations. Most often the bone marrow is responding to a demand elsewhere in the body and releasing granulocytes before they fully mature. Less often, the marrow itself is producing cells abnormally. The reactive explanations are far more common. [6]

Usually temporary causes

• Infection. Acute infection is the classic reason. When the body mobilizes neutrophils quickly, less mature cells are released into the blood, which clinicians call a “left shift.” [1] [3]
• Inflammation. Inflammatory conditions and flares can raise IG without any infection. [1]
• Recent surgery, injury, or bleeding. Tissue injury and acute blood loss are both associated with immature granulocytes in the blood. [1] Physical stressors such as surgery, trauma, and burns also raise the white count through release from bone marrow stores. [3]
• Pregnancy. Immature granulocytes can appear in the blood during pregnancy and in newborns as part of a normal physiological state. [1] In these cases they reflect a healthy bone marrow response. [2] The total white count also rises gradually through pregnancy, so pregnancy results are read against pregnancy-specific expectations. [3]
• Corticosteroids. Steroid medicines such as prednisone and dexamethasone raise the white count. [3] Part of that rise comes from faster release of neutrophils from the bone marrow, and a case report describes a jump in immature (band) neutrophils after a single dose of dexamethasone in a patient with no infection. [5] Do not stop a prescribed steroid on your own; talk to the prescribing clinician.
• Growth-factor medicines. Drugs that stimulate white cell production, such as G-CSF, raise IG as an expected effect. [1]

Less common causes

Immature granulocytes are also found with blood cancers and other disorders of the bone marrow, and with some cancers outside the blood. [1] These are the reason a persistent, unexplained result is followed up rather than ignored. They are not the usual explanation for a single flag.

When a high IG result needs follow-up

The difference between a result to watch and a result to act on is mostly about the company it keeps and whether it goes away.

A transient rise has a likely trigger, sits alongside an otherwise unremarkable count, and settles on a repeat test once the trigger has passed. That is the common pattern.

A persistent or marked rise needs a conversation with your doctor. The features that change the picture are:

• other abnormal counts on the same report, such as anemia, low or high platelets, or a very high or very low white count. Abnormal red cells or platelets alongside a raised white count suggest a primary bone marrow process and should prompt hematology evaluation. [3]
• an IG result that is well above your lab’s upper limit, or rising across repeat tests;
• a high IG with no infection, inflammation, injury, pregnancy, or medication to explain it;
• symptoms such as unexplained fever, weight loss, drenching night sweats, easy bruising, or an enlarged spleen. [3]

Get emergency care right away, by calling 911 or going to an emergency department, for new confusion or severe difficulty breathing. Do the same if you have an infection, or feel acutely unwell with a fever, and develop a racing heart or shivering and feeling very cold. This applies whatever your IG result says. These can be signs of sepsis, which is a life-threatening medical emergency. [7]

The bone marrow question

Many people searching for this result are really asking whether it means a bone marrow problem or leukemia. For an isolated finding, the usual answer is repeat testing, and a bone marrow biopsy is almost never needed. [6] Research on IG in myeloid bone marrow disorders was carried out in patients already diagnosed with those disorders. [1] It does not show that a small, isolated IG rise in an otherwise normal blood count points to one.

If your doctor does want to look further, the usual first steps are a repeat complete blood count with differential and a review of a blood smear under the microscope. [3] A referral to a hematologist, and any bone marrow testing, comes after those steps point that way, not from a single IG line.

A small IG flag that stays high for months

A common version of this question is a small absolute value, for example an Immature Grans (Abs) of 0.04 when the lab’s printed upper limit sits just below it, that is flagged high on every CBC for months while everything else looks normal.

Read that pattern on its own terms:

• Stability matters more than the flag. A value that sits at the same small level for months is a different finding from one that climbs from test to test.
• Check the rest of the report each time. If the white count, neutrophils, hemoglobin, and platelets stay within your lab’s ranges, a small stable IG rise has a very different meaning from one paired with other abnormal counts, which is the pattern that suggests a bone marrow process. [3]
• Look for an ongoing trigger. An inflammatory condition, a long-running infection, regular steroid use, pregnancy, or recent procedures can each keep IG slightly raised. [1]
• Keep the draws comparable. A small absolute value can move from one lab or analyzer to another, so trends are easiest to read when repeat tests come from the same lab. [4]

Bring the whole series of results to your doctor rather than the latest one alone. A persistent flag with no explanation is worth one clinical look, even when the number is small. That look usually means reviewing the trend, checking for a trigger, and deciding whether a smear or other tests are needed.

Reading IG alongside your WBC, neutrophils, and the rest of the differential

An IG result is one line in a differential, and the lines around it change what it means.

High IG with high neutrophils and a high white count. This is the textbook picture of the bone marrow answering a demand, most often an infection, inflammation, or physical stress. Release of less mature cells into the blood produces the “left shift” pattern. [3] For the wider picture, see what a high white blood cell count means, the white blood cell count reference, and the neutrophils reference.

High IG with a normal white count and normal neutrophils. Often a small, early, or resolving response. Check the absolute IG before the percentage, then look for a recent trigger and repeat the test once it has passed.

High IG% with a low white count. Because the percentage is a share of the total, a low total can push IG% up even when the absolute number is small. [3] A genuinely low white count or low neutrophil count is its own finding and worth raising with your doctor.

High IG with anemia or abnormal platelets. This is the combination that suggests the bone marrow itself should be looked at, and it is a reason for prompt follow-up rather than routine retesting. [3]

For how the five main white blood cell types relate to each other, see the WBC differential explainer. If a lymphocyte line is also flagged, the companion article on high lymphocytes covers that side.

Is high IG the same as high granulocytes?

No. “Granulocytes” is the family of mature neutrophils, eosinophils, and basophils, and a high total granulocyte count is mostly a high neutrophil count. That is usually driven by infection, stress, smoking, or medicines such as corticosteroids. [3] The IG line counts only the immature stages of that family. [1] You can have a high neutrophil count with a normal IG, or a small IG rise with a normal neutrophil count.

Why some reports list immature granulocytes and others do not

Whether an IG line appears depends on your lab’s analyzer and reporting rules, not on your health.

Some modern hematology analyzers count immature granulocytes automatically and report them as an extra line of the differential. [4] Other setups do not report IG as its own line. When the analyzer flags possible immature cells, the lab may review a blood smear under the microscope instead, and a manual review reports the individual stages (such as metamyelocytes or myelocytes) or bands, or a comment such as “left shift.” [4] [3] Labs also set their own rules for when an automated IG result is released directly and when it triggers a smear review. [4]

So an earlier report with no IG line does not mean you had none, and a new report that suddenly shows IG does not mean something new has happened. It may simply be a different lab or instrument. The reverse also applies: a manual smear and an automated count can give slightly different numbers for the same blood. [4]

When to retest, and what to do next

Start by confirming the result. Evaluation of a raised white count begins with a repeat complete blood count with differential and a review of a blood smear. [3] Time the repeat so it answers the question: after any infection, flare, or procedure has settled, and at a point in a steroid course your prescriber agrees on. A result that has come back to your lab’s range needs nothing further. A result that is still high, or that has other lines flagged with it, goes to your doctor with both reports side by side.

The Complete Blood Count (CBC) with Differential and Platelet Count Test is the right test for that repeat, because it reports the white count and the differential together with red cells and platelets, which is the combination the patterns above depend on. Whether the report includes a separate IG line depends on the lab that runs it. Mito members pay our cost for lab tests. For a walk-through of every line on the report, see how to read CBC results.

Testing is not a substitute for evaluation. If the result is rising, comes with other abnormal counts, or comes with symptoms, book time with your doctor rather than ordering another panel.

Bottom line

A high immature granulocyte result usually means the bone marrow is releasing young white cells early in response to infection, inflammation, injury, pregnancy, or a steroid medicine. [1] Compare it with the range printed on your own report, read the absolute line alongside the white count and the rest of the differential, and repeat the test once any trigger has passed. Follow up with your doctor when the result persists without an explanation, keeps rising, or appears with other abnormal counts or symptoms.

Sources

1. Lu Q, et al. Evaluation of immature granulocyte parameters in myeloid neoplasms assayed by Sysmex XN hematology analyzer. Journal of Hematopathology (2022)
2. Cleveland Clinic: Granulocytes
3. American Family Physician: Evaluation of Patients with Leukocytosis (2015)
4. Linko-Parvinen AM, et al. Accuracy of Sysmex XN immature granulocyte percentage compared to manual microscopy. Journal of Laboratory and Precision Medicine (2021)
5. Moore J, Schiffman F. Corticosteroids and Bandemia: A Case Report and Review of the Literature. Journal of Brown Hospital Medicine
6. The Blood Project: For Clinicians, Explaining Immature Granulocytes
7. CDC: About Sepsis

Photo by Hamish Duncan on Unsplash.