Rheumatoid factor test: what the RF result means
By the titre method, a value lower than 1:80 is considered normal (UCSF Health)
- Updated
- 2026-09-10
- Every number with its source
What rheumatoid factor is
Rheumatoid factor (RF) is an antibody that the immune system sometimes produces against the body's own proteins. In the blood of healthy people RF is usually absent or present only in very small amounts, but a raised level is often associated with rheumatoid arthritis — a chronic inflammatory joint disease. The RF test is not the only way to diagnose rheumatoid arthritis: some people with the disease have a negative RF result, and some people whose RF is raised do not have rheumatoid arthritis. That is why doctors usually assess RF together with other tests — for example, antibodies against cyclic citrullinated peptide (anti-CCP) and inflammation markers such as C-reactive protein (CRP). RF can also be raised in other autoimmune diseases or chronic infections, so this test alone does not establish a diagnosis — the result is always interpreted by a doctor together with the symptoms and other tests.
Reference range
| Result | Value, IU/mL | Source |
|---|---|---|
| Negative (normal) result — general By the titre method, a value lower than 1:80 is considered normal (UCSF Health) | less than 15 | UCSF accessed 2026-09-06 |
Every laboratory states its own reference limit, so the exact figure and the units (most often IU/ml) have to be looked up on your own result form. RF alone does not establish a diagnosis: the result is interpreted by a doctor together with the symptoms and other tests.
When the test is done
- When there is joint pain or stiffness that is worse in the morning or after a longer period without moving
- When the joints are tender to the touch, red, warm or swollen
- When tiredness, fever or a reduced appetite occur alongside
- When rheumatoid arthritis or another autoimmune disease is suspected
- When firmer lumps are noticed under the skin near the joints
- When checking, together with other tests, for a chronic infection or some cancers
How to prepare
- No special preparation is needed for this test — there is no need to fast or to change your usual daily routine
A raised (positive) RF
A raised (positive) RF is often associated with rheumatoid arthritis, but it can also indicate other autoimmune diseases, chronic infections or some cancers. A positive result on its own does not confirm a diagnosis — it is assessed together with the symptoms, anti-CCP and other tests.
Possible causes of a raised result
- Rheumatoid arthritis or other autoimmune diseases
- Sjögren's syndrome, systemic lupus erythematosus (lupus), scleroderma, juvenile idiopathic arthritis
- Chronic infections — hepatitis C, tuberculosis, endocarditis
- Some cancers, for example leukaemia
Symptoms that may accompany a raised result
- Joint pain or stiffness, worse in the morning or after a longer period without moving
- Joint tenderness, redness, warmth
- Joint swelling
- Tiredness, fever, a reduced appetite
- Firmer lumps under the skin near the joints
What to discuss with a doctor
- An anti-CCP test and inflammation markers (CRP, ESR) — they help to assess the likelihood of rheumatoid arthritis more accurately
- How long the symptoms have lasted and the nature of the joint involvement — important for the differential diagnosis
- Whether there are signs pointing to another autoimmune disease or a chronic infection
- When to repeat the test while the course of the condition is being monitored
A negative (normal) RF
Per MedlinePlus, a negative (normal) result means that there is no RF in the blood or only very little of it. It does not remove the possibility of rheumatoid arthritis: some people with rheumatoid arthritis have a negative RF result, which is why doctors often also order an anti-CCP test and assess the symptoms as well as other markers.
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Frequently asked questions
›What is the normal rheumatoid factor level?
Per MedlinePlus, a negative (normal) result means that there is no RF in the blood or only very little of it. Every laboratory states its own reference limit on the result form, so the exact figure and the units (most often IU/ml) have to be looked up on your own test result.
›Does a positive RF mean I have rheumatoid arthritis?
Not necessarily. A positive RF is often associated with rheumatoid arthritis, but it can also indicate other autoimmune diseases, chronic infections or some cancers. Some healthy people can also have a positive RF, so the result needs to be discussed with a doctor together with the symptoms and other tests.
›Does a negative RF rule out rheumatoid arthritis?
No. Some people with rheumatoid arthritis have a negative RF result, so doctors often order an anti-CCP test alongside it and assess the symptoms as well as other markers.
›How does RF differ from the anti-CCP test?
Both tests are used when rheumatoid arthritis is suspected, but anti-CCP is considered more specific to this disease, while RF can also be raised in other autoimmune diseases or infections. That is why doctors often assess them together.
›Do you need any special preparation before an RF test?
No, per MedlinePlus no special preparation is needed for this test — you do not have to fast or change your usual daily routine before the blood draw.
›Which symptoms may mean it is worth having an RF test?
Joint pain or stiffness, especially worse in the morning, joint swelling, redness or warmth, and also tiredness or fever — such symptoms can be a reason for a doctor to order RF and other tests related to rheumatoid arthritis.
Sources
Related markers
This site is not an emergency service. If severe chest or head pain, breathlessness, confusion, difficulty speaking, heavy bleeding or another acute problem has come on suddenly — do not wait for tests, call 112.
This information is not a diagnosis and does not replace a consultation with a doctor. Reference ranges depend on the laboratory, your age and sex — always compare your result with the range printed on your own report.