###1: Reticulocytes/Red Blood Cells [Number Fraction] in Blood by Automated Count
###3: This automated blood test measures the fraction of red blood cells that are reticulocytes, which are newly produced, immature red blood cells released by the bone marrow.
["###4: The reticulocyte fraction helps clinicians evaluate bone marrow blood-cell production and can provide context when assessing anemia or monitoring treatment."]
Key facts at a glance
- LOINC
- 17849-1
- Short code
- Retics/RBC NFr Auto
- Synonyms
- Retics/RBC NFr Auto
- Category
- chemistry
- Sample
- whole-blood
- Container
- Lavender-top (EDTA)
- Units
- N/A
- Ref low
- 4.2
- Ref high
- 5.9
- Critical range
- 2 N/A – 7 N/A
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 18–65 years
- Method
- automated-count
- CPT
- 85041
- SNOMED
- 900000000000003001
- Specimen volume
- 3 mL
- Stability
- Room temperature: 4h, Refrigerated: 24h
- Hemolysis max
- 0
- Lipemia max
- 0
- Icterus max
- 0
- TAT
- 4–24 hours
- Order
- routine
###5: What this test measures
###6: The test estimates what proportion of circulating red blood cells are reticulocytes. Because reticulocytes mature into mature red blood cells over time, a higher or lower fraction can reflect changes in blood-cell production or red blood cell lifespan.
###7: Why reticulocytes matter
###8: Reticulocytes are immature red blood cells produced in the bone marrow. Their presence allows clinicians to assess whether the marrow is responding appropriately to anemia, blood loss, treatment, or another change affecting red blood cells.
###9: How the result is interpreted
###10: The reticulocyte fraction is interpreted together with the complete blood count, hemoglobin, red blood cell indices, symptoms, medical history, and other laboratory results. The pattern of change over time is often more informative than a single result.
###11: Factors that may affect the result
###12: Recent blood transfusion, bleeding, pregnancy, kidney disease, nutritional deficiencies, medications, and treatment for anemia can influence reticulocyte levels. Timing of specimen collection and recent changes in therapy may also affect interpretation.
Reference range
Adult males: 4.2-5.9; Females: 3.8-5.1 x 10^12/LN/A
No special preparation required. Stay well hydrated.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
###13: Clinically, an increased reticulocyte fraction may suggest an appropriate marrow response to blood loss or treatment of deficient red blood cell production, while a decreased or inappropriately low fraction may suggest impaired production. The result is not diagnostic by itself and must be interpreted by a qualified healthcare professional in the patient's clinical context.
Short name
###2: Automated reticulocyte fraction
Frequently asked questions
###14: Is this the same as a routine complete blood count?
###16: Does a low result always mean the bone marrow is not working?
###18: Why might the result change after treatment for anemia?
Sources
- 1
- 2Lab Tests OnlineSource
- 3
Click any link to access the full source. PubMed Central (PMC) links provide free full-text access.
This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.
This content is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you have about a medical condition, and never disregard professional medical advice or delay seeking it because of something you read here.
If you think you may have a medical emergency, call your local emergency number or go to the nearest emergency department immediately.
Medically reviewed by WellAlly Editorial Team Last reviewed August 17, 2026. · Read our editorial policy