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Reticulocytes: Normal, High & Low Counts

Written by Biljana Novkovic, PhD | Last updated:
Jonathan Ritter
Puya Yazdi
Medically reviewed by
Jonathan Ritter, PharmD, PhD (Pharmacology), Puya Yazdi, MD | Written by Biljana Novkovic, PhD | Last updated:

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Reticulocytes, or immature red blood cells, can tell your doctor how well your bone marrow is working. They can help zero in on underlying health issues or tell if certain therapies are working. Keep reading to learn more about high and low reticulocyte counts and their effects on your health.

What are Reticulocytes?

Reticulocytes are newly formed immature red blood cells. They are produced in the bone marrow [1].

Normally, doctors use a reticulocyte test to look at bone marrow function. That’s because reticulocytes are a good indicator of the bone marrow’s ability to produce red blood cells [1, 2].

Reticulocyte Test

Reticulocyte count or percentage is a good indicator of the bone marrow’s ability to produce enough red blood cells (erythropoiesis).

Your doctor may order this test if you have signs of anemia (low red blood cell count, low hemoglobin, or low hematocrit) [1, 2].

Your doctor may order a reticulocyte test to [3]:

  • Help find out the cause of anemia, after an abnormal blood test
  • Find out whether bone marrow is functioning properly
  • Monitor response to a treatment, such as treatment for specific types of anemia
  • Check bone marrow function after chemo or radiation therapy
  • Monitor the function of bone marrow after a bone marrow transplant

Because there are many diseases and conditions that can affect red blood cell production and bone marrow function, a reticulocyte test can indicate something may be wrong but it cannot be used to diagnose a particular disease on its own [1, 2].

Your doctor will interpret this test, taking into account your medical history, signs and symptoms, and other test results.

Normal Range

Normally, reticulocytes make up 0.5 – 1.5 % of red blood cells (up to 2.6% according to some laboratories). The values are higher in infants, ranging from 2 – 6%.

Absolute reticulocyte counts normally range from 20 – 80 thousand cells/uL (cells per microliter).

There is some lab-to-lab variability in ranges due to differences in equipment, techniques, and chemicals used.

Low Reticulocyte Count

When reticulocyte count is low, that means that the production of red blood cells is decreased.

Causes shown below are commonly associated with low reticulocytes. Work with your doctor or another health care professional to get an accurate diagnosis. Your doctor will interpret this test, taking into account your medical history, signs and symptoms, and other test results.

Causes

1) Abnormal Bone Marrow Function

Decreased reticulocyte count (medically known as reticulocytopenia), can be a result of abnormal or suppressed bone marrow function. Bone marrow issues can be caused by infections, injury, or cancer [1].

There are also bone marrow disorders that impair red blood cell production, such as aplastic anemia [1, 4].

In addition, bone marrow function can be decreased as a result of cancer therapy (chemo or radiation therapy) [1, 5].

2) Nutritional Deficiencies

A low reticulocyte count can be an indicator of various anemias [1, 4].

Nutrient deficiencies that cause anemia, such as iron, folate, or vitamin B12 deficiency can decrease your reticulocyte count [6, 7, 1].

3) Alcoholism

Alcoholism and alcohol abuse can decrease reticulocyte count [8, 1].

4) Viral infections

Viral infections can cause your reticulocyte count to temporarily decrease [9].

5) Kidney Disease

Erythropoietin is a hormone made in the kidneys that travels to the bone marrow where it stimulates the production of red blood cells.

In kidney disease, the production of erythropoietin decreases, which reduces the red blood cell production. That is why kidney disease can be linked to a decreased reticulocyte count [10, 11].

6) Liver Disease

Liver disease can impair the production of red blood cells, resulting in a lower reticulocyte count [1].

Symptoms

Low reticulocytes do not cause any symptoms in and of themselves.

However, people with low reticulocytes may experience symptoms associated with anemia, such as:

  • Fatigue
  • Dizziness/headaches
  • Chest pain
  • Shortness of breath
  • Pale skin

Increasing Reticulocytes

Low reticulocytes are a sign of an underlying disorder or disease. The most important thing is to work with your doctor to find out what’s causing your low reticulocytes and to treat any underlying conditions.

Discuss the additional lifestyle changes listed below with your doctor. None of these strategies should ever be done in place of what your doctor recommends or prescribes!

Maintain a healthy, well-balanced diet. A deficiency in nutrients, such as iron, folate, and vitamin B12 can decrease red blood cell production [1]. However, deficiencies of these nutrients may have non-dietary causes, such as bleeding or gut issues (malabsorption), in which case they can’t be corrected by simple dietary changes.

Your doctor will prescribe supplements if needed, to correct any dietary deficiencies and insufficiencies.

Excessive alcohol consumption can decrease reticulocyte counts, by causing liver disease and depleting nutrients needed for red blood cell production. Reduce or eliminate alcohol until your condition improves. Discuss your alcohol consumption with your doctor [8, 1].

High Reticulocyte Count

When reticulocyte count is high, that means that the production of red blood cells is increased.

Causes shown below are commonly associated with high reticulocytes. Work with your doctor or another health care professional to get an accurate diagnosis. Your doctor will interpret this test, taking into account your medical history, signs and symptoms, and other test results.

Causes

1) Blood Loss

A high reticulocyte count (medically known as reticulocytosis) can be found after blood loss due to injury, ulcers, or surgery.

Bone marrow will compensate for blood loss by increasing red blood cell production. However, when lots of new cells are produced, bone marrow can release them before they have fully matured, which increases reticulocyte levels in the blood in the short-term. Reticulocytes eventually decrease back to normal [1].

2) Hemolysis

Reticulocytes increase when there is increased red blood cell destruction (hemolysis). When there aren’t enough red blood cells in the body, bone marrow tries to compensate by increasing red blood cell production [1, 12].

For example, increased red blood cell destruction and high reticulocyte counts occur in sickle cell disease [1, 13].

3) Endurance Exercise

Athletes may have increased reticulocytes due to exercise. Exercise increases cortisol and other stress hormones, which in turn stimulate reticulocyte release from the bone marrow [14, 15].

4) Toxins

Exposure to toxins such as ethylene glycol ethers, common ingredients in paints and cleaners, can increase reticulocyte counts. In an observational study of 34 screen-printing workers, the people who were exposed to the toxins had significantly higher reticulocyte counts [16].

Lead is another toxin that can increase reticulocytes [17].

5) Smoking

Smoking can also increase reticulocyte counts [18].

6) Pregnancy

Reticulocyte counts can be normally increased in pregnancy [19].

7) Overproduction of Red Blood Cells

Polycythemia vera is a condition in which there is higher red blood cell production. It is linked to higher reticulocyte counts [20].

Erythroid leukemia, a rare form of acute myeloid leukemia, causes higher reticulocyte production and release [21].

Tumors that increase erythropoietin levels can increase reticulocytes by signaling the bone marrow to make more red blood cells.

8) Erythropoietin Therapy/Doping

Reticulocytes can also increase in erythropoietin therapy or doping [22, 23].

9) Treatment for Anemia or Recovery After Cancer Therapy

When the body is missing nutrients, bone marrow can’t produce enough red blood cells. However, when those nutrients become available, the bone marrow compensates by increasing the rate of red blood cell production until red blood cell levels return back to normal [1].

Reticulocytes will also gradually increase after chemotherapy or radiation therapy, as bone marrow recovers [1].

Decreasing Reticulocytes

High reticulocytes are usually a sign of an underlying disorder or disease. The most important thing is to work with your doctor to find out what’s causing your low reticulocytes and to treat any underlying conditions.

Quit smoking. This can prevent your reticulocytes from being elevated [18].

About the Author

Biljana Novkovic

Biljana Novkovic

PhD
Biljana received her PhD from Hokkaido University.
Before joining SelfHacked, she was a research scientist with extensive field and laboratory experience. She spent 4 years reviewing the scientific literature on supplements, lab tests and other areas of health sciences. She is passionate about releasing the most accurate science and health information available on topics, and she's meticulous when writing and reviewing articles to make sure the science is sound. She believes that SelfHacked has the best science that is also layperson-friendly on the web.

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