Home › Biomarkers › Rheumatoid factor
Rheumatoid factor is a protein made by your immune system. Little or no rheumatoid factor is considered normal, while a higher value, together with symptoms, can point to an autoimmune condition or another condition.[1]
On this page you can read what rheumatoid factor is, what the guidelines say about a value that is too low or too high, what affects your value and which values are best read alongside it.
Also known as: RF blood test. At the lab: RF.
Normally your immune system makes proteins called antibodies, which attack pathogens. Rheumatoid factor does not do that. It attacks healthy cells, usually IgG, one of the most common antibodies.[1]
Your immune system makes rheumatoid factor by mistake, or when it works extra hard against pathogens.[1]
Doctors usually use rheumatoid factor together with other tests. This helps them detect an autoimmune condition of the joints, a long-term condition that can also affect organs.[1]
The test can also help when looking for other autoimmune conditions, long-term conditions of the liver, lungs or heart, and certain blood conditions.[1]
People with this joint condition often have anaemia. So if you have anaemia, your doctor may also look at rheumatoid factor.[1]
Rheumatoid factor plays no part in wear and tear of the joints. That wear and tear is not an autoimmune condition.[1]
Labplusarts, the lab BioProfile works with, uses a range of 0 to 14 ku/l for rheumatoid factor. The lab calls a value within those limits normal.[2]
| Result | What it can mean | Who it is for |
|---|---|---|
| Negative (normal)[1] | Little or no rheumatoid factor in your blood; does not rule out a joint condition | Everyone who takes the test |
| Positive (abnormal)[1] | More rheumatoid factor in your blood; can point to an autoimmune condition or another condition | Everyone who takes the test, assessed together with symptoms |
| An amount[1] | The higher the value, the greater the chance of a condition linked to rheumatoid factor | When the lab reports an amount with its own normal range |
Source: MedlinePlus, U.S. National Library of Medicine, on the rheumatoid factor test in general.[1]
Little or no rheumatoid factor is called a normal result. Even so, that does not rule out a joint condition. If you do have symptoms, your doctor may request more tests.[1]
A higher value can point to an autoimmune condition, long-term inflammation or certain other conditions. But even a high value is not always a sign of a condition. Your doctor looks at your symptoms, your medical history and other tests, and may refer you to a rheumatologist.[1]
BioProfile is working on its own zones for each value, from risk to optimal. A doctor reviews those zones before they appear in your result.
Your immune system makes more rheumatoid factor when it works extra hard against pathogens, or by mistake in an autoimmune condition.[1]
Long-term conditions of the liver, lungs or heart can go together with a higher rheumatoid factor.[1]
You do not need to prepare in any special way for the test.[1]
Rheumatoid factor is included in BioProfile 121 and 150.[3]
The BioProfile editorial team wrote this page on 10 October 2026 from the sources below, which we read on 10 October 2026. Every number on this page appears in one of those sources, with that source's number next to it. An expert has yet to check this page; after that check, the expert's name and the date of the check will appear at the top. This page offers explanation, not a diagnosis. Discuss a value outside the range with your GP.
