Rheumatoid Factor (RF)
Rheumatoid factor is an antibody targeting the Fc portion of IgG and is positive in most patients with rheumatoid arthritis. It is not specific and can also occur in Sjogren syndrome, cryoglobulinemia, chronic infections such as hepatitis C and endocarditis, and in some healthy older adults. Higher titers correlate with more aggressive rheumatoid disease.
Optimal range: who says what
No institution or named practitioner we track states an optimal target for Rheumatoid Factor (RF). How we verify ranges.
- No stated targetNo separate optimal establishedA result below the lab's negative cutoff is expected; RF is a diagnostic marker, not a value to optimize
- Lab reference interval<14 IU/mL, Weakly positive: 14-40 IU/mL, Positive: >40 IU/mLWhat a lab report flags against. A lab interval is not an optimal target.
5 providers include this
Autoimmune Markers
Why Rheumatoid Factor (RF) matters
Elevated in 70-80% of rheumatoid arthritis cases. Also positive in other autoimmune diseases. Used for diagnosis and prognosis.
Which Providers Test Rheumatoid Factor (RF)?
Cheapest: Mito Health at $297/year. Most comprehensive: Function Health, 160+ biomarkers for $365/year.
5 panels that include it, cheapest first
| Provider | Annual Cost | Total Biomarkers | $/Biomarker |
|---|---|---|---|
| $297 | 100+ | $2.97 | |
 Superpower | $349 | 100+ | $3.49 |
 Function Health | $365 | 160+ | $2.28 |
| $365 | 100+ | $3.65 | |
| $499 | 100+ | $4.99 |
$/Biomarker is annual cost divided by the panel's advertised biomarker count, not the price of this one test. We track 23 blood test providers (32 plans); 21 of those plans are itemized marker by marker. Compare all of them.
16 itemized panels do not include Rheumatoid Factor (RF)
WHOOP Advanced Labs · Labcorp OnDemand · Life Extension Elite · Everlywell · InsideTracker · Marek Health Base · Marek Health Comprehensive · Marek Health Complete · Marek Health Executive · Empirical Health · Oura Health Panels · SiPhox Health · Hims Labs · Healthspan · Vitality Blueprint Standard · Vitality Blueprint Elite
11 providers not itemized in our matrix
We have not itemized these marker by marker (some sell tests one at a time), so this page cannot say whether they offer Rheumatoid Factor (RF). Check with them directly.
Life Extension Standard · Quest Health · Ultrahuman Blood Vision · Lifeforce · Hundred Health · Personalabs · Walk-In Lab · HealthLabs · WHOOP Specialized Panels · Marek Health Essential · Vitality Blueprint Upload
Experts discussing Rheumatoid Factor (RF)
Podcast episodes where clinicians and researchers cover this marker in depth. Curated by hand; an episode is listed only when the marker is a substantial topic, not a passing mention.
- Healing Autoimmune Disease Using A Functional Medicine ApproachDisclosure: Hyman co-founded Function Health, which appears in our blood-test comparisons.
- #399 - Wisely Ordering Autoantibodies (ACP IM 2023)
- #147 - Rheumatoid Arthritis for the Internist
Frequently Asked Questions
What is the optimal range for Rheumatoid Factor (RF)?
No separate optimal established: A result below the lab's negative cutoff is expected; RF is a diagnostic marker, not a value to optimize. Lab reference interval: <14 IU/mL, Weakly positive: 14-40 IU/mL, Positive: >40 IU/mL. That is what a lab report flags against, not an optimal target.
Which blood test providers include Rheumatoid Factor (RF)?
5 of the 21 blood testing panels we itemize marker by marker include Rheumatoid Factor (RF) in their panels. This biomarker has limited availability.
Medical Disclaimer
This information is for educational purposes only and is not medical advice. Always consult with a qualified healthcare provider about your specific health needs.
Last reviewed Sep 23, 2026 · First published Sep 30, 2025