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Reticulocyte Count (Absolute)

The number of reticulocytes (very young red blood cells) in a set amount of blood. It shows how many new red cells your bone marrow is releasing.

AI-verified against cited sources. Awaiting expert reviewAlso called RET#, ARCLOINC 60474-4

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What it is

Reticulocytes are young red blood cells that have just left the bone marrow. This result is the actual number of them in your blood, not a percentage. Labs usually work it out by multiplying the reticulocyte percentage by your red blood cell count, and many analyzers report it directly. The same value can be printed in several unit styles, such as 50 (×10⁹/L, the same as K/µL), 0.05 (million per µL) or 50,000 (cells per µL).

Why it matters

Because it is a count and not a percentage, this number is less misleading when you have anemia. In anemia the reticulocyte percentage can look high only because the total number of red cells is low. The absolute count avoids that problem and shows more clearly whether your bone marrow is making enough new red cells. Clinicians use it with your hemoglobin to help sort out the causes of anemia and to follow recovery after treatment. On its own it doesn't point to a cause.

If it’s low

A lower-than-usual count means your bone marrow is releasing fewer new red cells than expected. If your hemoglobin is also low, that can point to a problem with making red cells rather than losing them. Your clinician reads it together with your hemoglobin, because the same count means different things depending on whether you have anemia.

Common causes

  • Low iron (iron deficiency anemia)
  • Low vitamin B12 or folate
  • Kidney disease
  • Scarring of the liver (cirrhosis)
  • Aplastic anemia or other bone marrow problems, including after chemotherapy or radiation
  • Some medicines

What can help

  • Ask your clinician whether iron, vitamin B12 and folate levels should be checked
  • Ask whether kidney or liver tests would help explain it
  • Eat a balanced diet that includes iron, B12 and folate foods, and keep up with routine checkups

If it’s high

A higher-than-usual count means your bone marrow is releasing new red cells faster than usual. That is a normal response when the body is making up for red cells it lost, for example after bleeding or when red cells break down early. It can also be a sign that treatment for anemia is working. Your clinician reads it together with your hemoglobin and other results.

Common causes

  • Recovery after treatment for low iron, vitamin B12 or folate (a sign the marrow is responding)
  • Pregnancy
  • A recent stay at high altitude
  • Some medicines
  • Recent or ongoing bleeding
  • Red cells breaking down faster than normal (hemolytic anemia)
  • Hemolytic disease of the newborn, in babies
  • A counting error from the analyzer, such as from blood parasites or fluorescent medicines

What can help

  • Ask your clinician whether your hemoglobin and other tests point to a cause
  • Ask whether a repeat test would help
  • Tell your clinician about recent bleeding, heavy periods, high-altitude travel or new medicines

Usual ranges

What labs print as the reference range, by who was tested. Ranges differ a little between labs, so the range on your own report is the one your result is judged against.

The usual range depends on age. Choose an age to see the one that applies.

Children and teens 4 ranges

See Retic # by age and sex, with the U.S. survey numbers where they exist.

What can affect your result

  • Anemia: a low red cell count lowers the absolute number of reticulocytes for the same marrow effort
  • Pregnancy and time at high altitude, which can raise the count
  • Age and sex: ranges differ in newborns and children, and some labs print a lower upper limit for women
  • The counting method and analyzer
  • Recent bleeding, a transfusion, or treatment for anemia
  • Some medicines
  • Malaria parasites, and some medicines that give off their own fluorescence, can make automated counts read falsely high. Fragments of red cells can make them read falsely low. Labs look at a blood film when the analyzer raises a flag.
  • Certain inclusions inside red cells, such as Heinz bodies or the Hb H inclusions of Hb H disease (a form of alpha thalassemia), can throw off automated counts.
  • Pregnancy, a recent move to high altitude, and some medicines can raise the count.
  • Recent blood loss, a blood transfusion, or treatment for anemia (such as iron, vitamin B12, folate or erythropoietin) can change the count within days.
  • Labs print this result in different unit styles (×10⁹/L, K/µL, ×10⁶/µL or cells/µL), and the numbers look very different even though they mean the same thing.

Changes within days, because reticulocytes spend only about 1 to 2 days in the blood before they mature.

When to talk to a clinician

Labs don't usually publish an urgent-call limit for this result. Contact a clinician if a high or low result comes with tiredness, shortness of breath, dizziness, a fast heartbeat, pale skin, or yellowing of the skin or eyes. Call 911 or your local emergency number for chest pain, severe shortness of breath, fainting or confusion.

Questions you could ask

  • How does my reticulocyte count fit with my hemoglobin?
  • Which unit is my lab using for this result?
  • Could recent bleeding or red cells breaking down faster explain this?
  • Is this a sign that my treatment is working?
  • Should we repeat it or add tests such as bilirubin?
  • Could low iron, B12 or folate explain this?

Questions people ask

Why does my report show a tiny number like 0.05?

Some labs print the reticulocyte count in millions per microliter (×10⁶/µL), so 0.05 means the same as 50 ×10⁹/L, or 50,000 cells per µL. Check the unit printed next to your result and compare it with the range printed on your report.

Is the absolute count better than the percentage?

It is often easier to interpret in anemia. The percentage can look high only because there are fewer red cells overall, while the absolute count shows how many new cells your bone marrow is actually releasing. Clinicians usually look at both, along with your hemoglobin.

Why do labs print different ranges for the absolute count?

Labs use different methods and analyzers, and some set separate limits for men and women. Mayo Clinic Laboratories lists 30.4 to 110.9 ×10⁹/L for adults, while other labs print limits between about 10 and 110 ×10⁹/L. Use the range on your own report.

Show the science and sources

Units

  • 1 ×10³/µL = 1 ×10³/µL
  • 1 ×10³/µL = 1 ×10⁹/L
  • 1 ×10³/µL = 0.001 ×10⁶/µL
  • 1 ×10³/µL = 1000 cells/µL

Open the Retic # unit converter

Is a change real?

Retic # naturally varies about 9.74% from test to test in the same healthy person. Between two results from the same lab, a change of roughly 30% or more is unlikely to be day-to-day noise or lab variation (95% reference change value). Source: Systematic review and meta-analysis of within-subject and between-subject biological variation estimates of 20 haematological parameters (Coskun A et al., EFLM WG-BV).

For clinicians and researchers

The absolute reticulocyte count is the reticulocyte percentage multiplied by the red cell count. LOINC lists a separate code for a calculated count (42758-3) and for automated (60474-4) and manual (40665-2) counts. Analyzers count reticulocytes by flow cytometry with RNA-binding fluorescent dyes, or labs count them by new methylene blue stain on a smear; Mayo reports the result in ×10⁹/L with a flow cytometry method. Unit styles vary by country and lab: ×10⁹/L is numerically identical to ×10³/µL, ×10⁶/µL (or 'mill/cmm') is 1,000 times smaller, and cells/µL is 1,000 times larger. Absolute counts are less affected by the denominator problem that inflates the percentage in anemia, and a reticulocyte production index or corrected count adds a hematocrit and maturation-time correction. Reference limits differ by method and sex: a 1996 study of 1,219 healthy people found different reticulocyte ranges for men and women over 20, and labs such as HNL and QEHB print a lower upper limit for women. In 5,692 Chinese adults on a Sysmex XN-B3, RET# and the other reticulocyte indices varied significantly by sex and age (BMC Cardiovasc Disord 2026). Automated counts can be spuriously high with malaria parasites or autofluorescent drugs, and spuriously low with red cell fragments (Clin Lab 2019). The same analyzers report the immature reticulocyte fraction and reticulocyte hemoglobin.

LOINC 60474-4 (primary), 14196-0, 40665-2, 42758-3. Specimen: whole-blood.

Sources

  1. Reticulocyte Profile, Blood (test RETB), Mayo Clinic Laboratories (catalog mirror at testcatalog.org)
  2. Sysmex Complete Blood Count Reference Ranges (March 2024), Vanderbilt Medical Laboratories (2024)
  3. CBC reference intervals (HEM-2597.01), Te Whatu Ora Health New Zealand, Waikato (2024)
  4. Haematology Adult Reference Ranges (HAE.N002, PUB_040), QEHB Pathology (2026)
  5. Hematology Reference Intervals (updated April 2026), HNL Lab Medicine (2026)
  6. Derivation of Russian-specific reference intervals for complete blood count, iron markers and related vitamins, PLoS One (2024)
  7. Reticulocyte Count, MedlinePlus (NIH National Library of Medicine)
  8. Reticulocytes: reference limits, Clinical and Laboratory Haematology (1996)
  9. Age- and sex-specific normative values for reticulocyte indices and their relation to early-stage CKM syndrome, BMC Cardiovascular Disorders (2026)
  10. Interferents of Automated Reticulocyte Analysis Integrated with Relevant Clinical Cases, Clinical Laboratory (2019)
  11. Heinz bodies interfere with automated reticulocyte counts, Haematologica (1999)
  12. Interference of Hb-H disease in automated reticulocyte counting, Clinical and Laboratory Haematology (1999)

AI-verified against cited sources. Awaiting expert review. Last reviewed 2026-10-03. How we build and check these pages.

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