If adults have nucleated red blood cells (NRBCs) in their blood, it’s usually a sign of a life threatening condition. The optimal NRBC count is 0. Even very low NRBC counts could cause a doctor to order further testing.

Nucleated red blood cells (NRBCs) are immature blood cells that have not completed development. They are not usually present at all in the circulating blood of adults. If you have NRBCs in your blood, it may indicate leukemia, certain blood disorders, or hypoxia (not enough oxygen in tissues).

Newborn babies have some NRBCs, which disappear from their bodies within the first few weeks of life. In adults, rapid blood loss or the destruction of many red blood cells in a short time can lead to a rapid increase in the production of red blood cells. In this case, your body may release NRBCs into your bloodstream.

This article will take a closer look at the NRBC blood test, including how to interpret results and what to expect after an irregular result.

If your doctor suspects certain conditions, they may order an NRBC blood test to check for the presence of these cells. But these cells are only indicators. This means that if these cells are in your blood, the doctor would order further testing to determine the underlying cause.

Some studies suggest that NRBCs may help guide doctors who treat intensive care (ICU) patients. One 2018 study found that NRBCs in ICU patients with acute respiratory distress syndrome (ARDS) were associated with more extended hospital stays and higher mortality rates.

Another study, published in 2023, looked at 800 critically ill patients being treated in the ICU. The presence of NRBCs was found to predict a higher mortality rate among people in this group.

During blood cell production, the red blood cell has a nucleus for only a very short time before expelling it. This process regularly occurs in the bone marrow before the blood cell circulates through the bloodstream.

Diseases of the blood can stress the bone marrow and cause it to release NRBCs into the blood. Why this happens is still unclear, although inflammation or hypoxia may be the root cause.

What conditions are associated with NRBCs?

NRBCs can indicate the presence of several diseases, including:

  • anemia
  • cancer
  • congestive heart failure
  • blood disorders

Since NRBCs should not be present in adults’ blood, your doctor may want to investigate any positive result. A positive result means that NRBCs have been found in the blood.

Labs can use different systems to measure the number of NRBCs in your blood. You may see either of the following:

Absolute value

This value reflects how many NRBCs are in a certain amount of blood. It’s usually listed as billions of NRBCs per liter (x 109/L) or NRBCs per microliter (/μL).

A doctor may consider your NRBC level to be elevated if it is higher than 0.02 x 109/L (20/μL). But some studies have an even lower threshold, ranging from 0.003 x 109/L (or 3/μL) to 0.01 x 109/L (10/μL).

A 2021 study of emergency department cases found that any count higher than zero (0/μL) could increase your risk of death. A similar 2017 study found that the risk of death increased as NRBC count increased.


You may also see your NRBC count expressed as a value compared with your number of white blood cells (WBCs). It’s either written as a value per 100 WBCs or as a percentage.

An ideal result would be 0.3/100 WBC (0.3%) or less. Anything higher might cause a doctor to perform further tests. But a 2016 study found that NRBC counts of 1.5/100 WBC (1.5%) or lower were usually not clinically significant. That means that if you had such a count, it wouldn’t necessarily reflect an underlying condition.

An NRBC blood test is part of a complete blood count (CBC) panel. A healthcare professional in your doctor’s office, a hospital, or a lab may perform this test.

The healthcare professional may first tie a rubber or elastic band around your upper arm. They will then insert a needle into your arm to collect a blood sample into a small vial. You may feel a small pinch when they insert or remove the needle.

They’ll then put a bandage over the insertion point or gauze tape around your arm to prevent any minor blood spotting. There may be slight bruising at the needle’s insertion spot.

The doctor’s office will call you with the results, or the doctor may review them at a follow-up appointment.

If your NRBC count is high, the doctor may order additional tests. These will depend on factors like your symptoms, other readings on the CBC blood test, and their working diagnosis.

Tests may include further lab tests or imaging studies like:

NRBCs are immature blood cells not typically present in the circulating blood of adults. When they appear on a blood test, they may indicate a blood disorder, one of several diseases, or a condition like hypoxia.

Since NRBCs don’t usually appear in the blood, doctors consider finding any NRBCs to be a possible cause for concern. But experts differ on what range is generally clinically significant.

An NRBC blood test is part of a complete blood count test. It requires taking a small blood sample from the arm, usually in a lab, doctor’s office, or hospital. If your test shows the presence of NRBCs, a doctor may order follow-up tests to look for one of several conditions based on other symptoms.