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Reticulocyte Production Index (RPI)

Published: August 9, 2026Updated: August 16, 2026

This test measures how efficiently your bone marrow is producing new red blood cells. It helps assess whether your body is making enough red blood cells to compensate for blood loss or other causes of anemia.

Quick summary

["The RPI helps doctors check if your bone marrow is working properly to replace lost red blood cells."]

Medically reviewed by WellAlly Editorial TeamLast reviewed August 16, 2026Editorial policy

Key facts at a glance

LOINC
31111-8
Short code
Reticulocyte production index
Synonyms
Reticulocyte production index
Category
hematology
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
CPT
85390
Specimen volume
5 mL
Stability
Room temperature: 4h, Refrigerated: 24h, Frozen: 7d
Hemolysis max
500
Lipemia max
1000
Icterus max
500
TAT
4–24 hours
Order
routine

What Is the RPI Used For?

Doctors use the RPI to diagnose and monitor conditions like anemia, especially when other blood tests (such as hemoglobin or reticulocyte counts) suggest the bone marrow isn’t producing enough red blood cells. It can also help evaluate responses to treatments like blood transfusions or medications.

How Is the RPI Calculated?

The RPI is derived from two blood tests: your reticulocyte count (a measure of immature red blood cells) and your hemoglobin level. It’s calculated to show whether your bone marrow is producing enough reticulocytes (early-stage red blood cells) to meet your body’s needs.

When Might You Need This Test?

You may need an RPI if your doctor suspects anemia due to conditions like iron deficiency, chronic disease, or after blood loss (e.g., from surgery or heavy menstrual bleeding). It’s also used to check if treatments for anemia are working correctly.

What Can Affect the RPI?

Several factors can influence the RPI, including medications (like chemotherapy or certain blood pressure drugs), chronic illnesses (such as kidney disease or liver problems), and recent blood loss. Stress, infections, or nutritional deficiencies (like vitamin B12 or folate) can also impact it.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

RPI

Frequently asked questions

Why do I need this test if I’m not feeling sick?
Even if you feel fine, your doctor may order this test to check for hidden causes of anemia or to monitor how well your body is producing red blood cells, especially if you’ve had recent blood tests or treatments.
What does a high or low RPI mean?
A low RPI suggests your bone marrow isn’t producing enough new red blood cells, which could mean anemia or a bone marrow disorder. A high RPI may indicate your body is overcompensating for blood loss or another condition affecting red blood cell production.
Can I affect my RPI results with diet or lifestyle?
Yes! Eating iron-rich foods (like lean meats or leafy greens), staying hydrated, and avoiding excessive alcohol or smoking can support healthy red blood cell production. However, your doctor should interpret results in the context of your overall health and medical history.
  1. 1
    MedlinePlus — Laboratory TestsSource
  2. 2
    Lab Tests OnlineSource
  3. 3
    Mayo Clinic — Tests & ProceduresSource

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.

Medical Disclaimer

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 16, 2026. · Read our editorial policy