What are Nucleated red blood cell (NRBC)?

Nucleated red blood cells (metarubricytes) represent the early stages of a red blood cell before it matures.

What are Nucleated Red Blood Cells (NRBC)

They are produced primarily in the bone marrow and are only occasionally observed in peripheral blood.

Nucleated Red Blood Cells NRBC
Nucleated Red Blood Cells NRBC

Nucleated RBCs (NRBC, normoblasts) are a very immature form of RBCs seen when there is a severe demand for RBCs to be released by the bone marrow or marrow involvement by fibrosis (=development of fibrous connective tissue as a reparative response to injury or damage) or a tumor.

By original: User:A. Rad, svg file drawn with FlashMX by birdyderivative work: RexxS (Hematopoiesis_(human)_diagram.svg) [CC-BY-SA-3.0 ( or GFDL (, via Wikimedia Commons
In healthy adult patients the NRBC count on a should be zero.

In those who are not in perfect health, the most important benefit of an NRBC count is to exclude a false high in the WBC count. Size-wise nucleated red blood cells are similar to lymphocytes. Because of that, many laboratory analyzers mislabel them and hence list a wrong lymphocyte and total white blood cell (WBC) count.

A NRBC count should also be performed routinely for all pediatric (=medical care of infants) and neonatal samples.



The information on is NOT intended to replace a one-on-one relationship with a qualified health care professional and is not intended as medical advice.

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