Canis ISSN: 2398-2942

Hematology: reticulocyte count

Contributor(s): Kathleen P Freeman


  • Immature form of RBC normally only present in bone marrow or in peripheral blood in low numbers.
  • Released into circulation when increased demand.
  • Reticulocytes appear in the blood 2-4 days after sudden blood loss. Therefore repeat sampling may be necessary.
  • To determine if anemia is regenerative or non-regenerative.
  • Other reticulocyte calculations are the absolute reticulocyte count and the reticulocyte production index (RPI).
  • Reticulocytes are best identified on supravital stains, eg new methylene blue stain.
    This may not be done routinely unless requested.
  • Polychromatophilic cells with Romanowsky stains are reticulocytes, but may underestimate response based on polychromasia alone.


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  • Cytological examination of supravitally stained blood smear.


  • Widely available at commercial laboratories.



  • Moderate to high.


  • Low.

Technique (intrinsic) limitations

  • Periodic filtering of NMB stain required to prevent precipitation that may be confused with reticulocytes.

Technician (extrinsic) limitations

  • Requires some experience for accurate identification of all reticulocytes.

Result Data

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Further Reading


Refereed papers

  • Recent references from VetMed Resource and PubMed.
  • Evans G O et al (1994) Reticulocyte counts in canine and rat blood made by flow cytometry. J Comp Pathol 111(1), 107-111.
  • Onishi T et al (1994) Changes of serum hemolytic activity and the number of reticulocytes in canine Babesia gibsoni infection. J Vet Med Sci 56(3), 611-612.

Other sources of information

  • Cowell R J, Tyler R D & Meinkoth J H (1999) Diagnostic Cytology and Hematology of the Dog and Cat. 2nd edn. St Louis: Mosby.
  • Duncan J R, Prasse K W & Mahaffey E A (1994) Veterinary Laboratory Medicine Clinical Pathology. 3rd edn. Ames, Iowa: Iowa University Press.
  • Jain N C (1993) Essentials of Veterinary Hematology. Philadelphia: Lea & Febiger.