What Are Immature Granulocytes (IG%)

What are immature granulocytes (IG%)

Immature granulocytes (IG) are young white blood cell forms that normally complete maturation in the bone marrow. When the body faces an infection or strong inflammatory process, the bone marrow accelerates production and releases some granulocytes into the blood earlier than usual. IG% shows the proportion of these immature forms among all leukocytes.

The marker is determined by automated haematology analysers and reported as a percentage.

Reference ranges

IG% in adults is typically up to 0.6%. Most healthy individuals have a result close to zero. Even a small increase above the reference range may have clinical significance, so this marker is evaluated carefully.

Why immature granulocytes may be elevated

An elevated IG% indicates increased bone marrow activity. The most common cause is acute bacterial infection. An IG% increase can be one of the first infection signals in the blood, sometimes noticeable before CRP or white blood cell count changes.

Other causes: acute inflammation (appendicitis, pancreatitis, peritonitis), tissue necrosis, severe trauma, burn injuries. Surgical intervention can temporarily raise IG%. During pregnancy, especially in the third trimester and during delivery, IG% physiologically increases.

Persistent and significant IG% elevation may be associated with haematological conditions — myeloproliferative diseases or myelodysplastic syndrome.

Why immature granulocytes may be low

Since the reference range is close to zero, a decrease has no clinical significance. An undetectable IG% is normal and indicates calm bone marrow activity.

What to do with your result

An elevated IG% prompts the doctor to evaluate possible infection or inflammation. Typically, CRP, procalcitonin, white blood cell differential, and clinical symptoms are assessed together. If infection is confirmed, treatment is prescribed. If the cause is unclear, the test can be repeated in a few days.

After infection or surgical intervention, IG% usually normalises within a few days to weeks.

Monitoring over time

IG% best reflects an acute process — it rises quickly and falls quickly. For long-term monitoring, it is less useful than, for example, CRP or white blood cells. However, if IG% is persistently elevated without a clear infection, the doctor may order additional haematological investigations.

Questions for your doctor

1. Does my elevated IG% indicate an active infection process? 2. Are additional inflammatory marker tests needed? 3. How do you evaluate IG% together with my other white blood cell differential results? 4. Is it worth repeating the test to check whether the marker has normalised?

*This is not medical advice. Consult your doctor regarding any health decisions.*