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Rheumatoid Factor

Published: July 27, 2026Updated: August 25, 2026

Rheumatoid Factor (RF) is an antibody that is often elevated in autoimmune conditions, particularly rheumatoid arthritis. It is used to aid in the diagnosis of inflammatory joint diseases.

Quick summary

RF is a key biomarker for diagnosing rheumatoid arthritis and other inflammatory conditions.

Medically reviewed by WellAlly Editorial TeamLast reviewed August 25, 2026Editorial policy

Key facts at a glance

Units
IU/mL
Clinical utility
diagnostic
Result kind
quantitative
FDA-cleared
Roche RF, Abbott RF, Siemens RF, Beckman RF
interpretation: {"text":"0–20 IU/mL: RF levels within this range are typically considered normal and are less likely to indicate rheumatoid arthritis or other inflammatory conditions.","label":"Normal"}; {"text":">20 IU/mL: Elevated RF levels may suggest the presence of an autoimmune disorder, such as rheumatoid arthritis, or other inflammatory conditions.","label":"Elevated"}

Rheumatoid Factor (RF) is an autoantibody that targets the Fc portion of immunoglobulin G (IgG). It is commonly found in the blood of individuals with rheumatoid arthritis, an autoimmune disorder characterized by chronic inflammation of the joints.

While RF is a valuable diagnostic tool, it is not specific to rheumatoid arthritis. Elevated levels can also be seen in other autoimmune diseases, chronic infections, and in some healthy individuals, particularly as they age.

The measurement of RF is often used in conjunction with other clinical findings and laboratory tests to support a diagnosis of inflammatory joint disease and to monitor disease activity over time.

Frequently asked questions

What does a high RF level mean?
A high RF level may indicate an autoimmune disorder like rheumatoid arthritis, but it is not definitive. Further tests and clinical evaluation are needed for a diagnosis.
Can RF levels change over time?
Yes, RF levels can fluctuate with disease activity. Monitoring RF levels can help assess the effectiveness of treatment and disease progression.
  1. 1
    Rheumatoid Factor (RF) TestSource
  2. 2
    Rheumatoid Arthritis DiagnosisSource

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 25, 2026. · Read our editorial policy